You have to be willing to have your whole sexual history discussed in front of a judge and jury. Then you have to prove several things..

1. That you got herpes from him and that it couldn't have possibly come from someone else. In other words, prove, in a court of law, that you didn't have it before you had sex with him and that there wasn't anyone else after him that you might have gotten it from.

2. You have to prove knowing intent on his part. He might argue that he didn't know he had it , or that he knew he had it, but his doctor told him that he wasn't contagious unless he was having an outbreak.

3. You have to prove that you didn't know he had it and still have consensual sex anyway.

The problem with cases like this, (No, I'm not a lawyer) is that these are often very difficult things to prove and you have to prove all of them. There's too much he said - she said.

One possible strategy you could use is to push for a settlement before it went to court, although, obviously you can't telegraph that to him. He has to think you're taking this all the way to a jury trial.

If it's revenge you're after, rather than the money, you might look into whether your state is one that treats knowingly infecting another person as a felony similar to assault and battery.

And honestly, the best revenge is simply success. This kind of guy is his own worst enemy and his bad karma will get him in the end anyway, without you having to do a thing. That worked for me with the woman that gave me herpes. I'm happy and with someone else and she's miserable and alone.

What sort of recourse are you looking for? Criminal or civil?

Criminal: Forget about it. The DA wherever you live is very unlikely to be interested in such a case. I don't know what state you're in, but it's very unlikely that you'll find a statute that covers this sort of behavior. Many states have statutes that criminalize the sexual transmission of HIV, but I know of none that does the same for herpes (a reflection of societal values about the relative dangers of the two viruses). Without such statutes, prosecutors have often charged people with HIV with attempted murder (in various guises, or murder if the "victim" has already died, or assault with a deadly weapon, where the virus or the body fluid has been construed as the weapon - a real stretch if you ask me!), but this will not fly for herpes, since you can't even infer an intent to kill since herpes is rarely fatal in the immunocompetent. Very few states would consider it an assault, and a decent defense attorney could rip that argument to pieces. For many statutes, you do not actually have to prove purpose (i.e. that it was his active desire to infect you); it is enough to show recklessness, which his behavior (substantial and unjustifiable risk of harming you) would usually qualify for - this is easier to show than that he "knowingly" did it, because he can easily say that he didn't know that he was likely to be transmitting the virus to you. There's just not likely to be a statute under which to prosecute it, no DA is really going to want to take it on. If you could even get a DA to pursue it, he'd most likely plead out for a slap on the wrist, but even if he were convicted, it would probably still just be a slap on the wrist.

Civil: Here, you have a shot (there have been suits on these grounds before, and at least one state appellate court has upheld the action). The standard of proof is lower (predonderance of evidence rather than beyond a reasonable doubt), and it's easier to find a claim that matches (economic damages for the lifetime costs of treating the infection, pain and suffering, perhaps punitive damages if his conduct is considered egregious. If he lied about having herpes, rather than simply failed to disclose, punitive damages are more likely). You might win, you might not.

The problems that Hugo pointed out exist, but are far from insurmountable:
There's a lot of judicial discretion here, but you wouldn't necessarily have to recount your sexual history. DNA fingerprinting could potentially provide the link between your ex and your virus, but it's expensive and you'd need a court order to force him to undergo the test. Under a civil standard, you don't have to prove it 100%, more like 51%. If he claims that he was not diagnosed until later (after you'd had sex), you'll probably be able to get a copy of his medical records during discovery to show otherwise. If he claims that his doctor told him he was not infectious, he has waived doctor-patient privilege and his doctor will have to back him up. If you're credible, your testimony is enough proof that you didn't know he had it.

This case certainly could be a lot of he-said, she-said, but so are many, many rape trials that end up in convictions (especially date-rape or acquaintance-rape). The outcomes of such cases are unpredictable, but to a large extent the societal pendulum has swung from "women are usually making this shit up" to "women are always telling the truth when they say they've been raped" (the truth is somewhere in the middle, but no one can doubt that most rape trials now strongly favor the victim whereas a few decades ago, they favored the accused). Whether you win will REALLY depend on the values of the people making the decision (judge and possibly jury): how strongly do they stigmatize people with herpes? How do they feel about issues of sexual responsibility and autonomy? Plenty of people in this country feel that in having unprotected sex outside of marriage, you get what you deserve (perhaps especially if you are a woman), and your ex would be crazy not to play into this and assert that you yourself are responsible for some of your damages (e.g. contributory negligence for failing to insist on condom use) and/or accepted the risk of contracting an STD by sleeping with him.

There are other problems. One of your first problems will be finding a lawyer who is interested in taking on such a case. Unless your ex is very wealthy, I wouldn't expect a lawyer to be particularly interested in such a case - the ambulance chasers are out for money, and most lawyers who offer free services will probably feel that there are people in more desperate need of assistance than you are (also, a lot of social-justice oriented lawyers probably are worried about slippery slopes in this sort of suit). The suit against Michael Vick (settled) was probably taken on because Vick was a millionaire. If you do end up pursuing this, though, you don't have to worry about how it will look if you seek a settlement - MOST cases result in settlement, and very few plaintiffs do not attempt to settle (those that do are usually trying to make a point or get publicity rather than recover damages). The problem is that your boyfriend's lawyer will know the problems with your case just as well as you do, so it'll be hard to psych out the other side.
If your ex is not wealthy, and you just want to teach him a lesson (rather than get real money off him), the place to do that is small claims court (known to most Americans because of shows like Judge Judy). You bring your own claim, no lawyer is required, evidentiary rules and procedures are greatly relaxed, it's cheap to file, and a judge (rather than a jury) decides the outcome. The downside is that there is a statutory maximum on damages - as low as $2000 in some states, as high as $7500 in others (you can google small claims court statutory maximum + your state). You can very rarely get more than this (I've heard of small-claims judges awarding $5000 per claim instead of $5000 per suit even when the claims were all related, but this is pretty rare. You go to small claims, and you shouldn't expect more than the statutory max on all your claims combined). I would say this is your best shot for punishing him, but there's still a good chance it won't go your way: small claims has a lot of judicial discretion, and a lot of judges will not want to give you anything for reasons I already mentioned briefly. It all depends on how they weigh his duty to disclose vs. your duty to protect yourself (an issue that will generally have little to do with the law, and more to do with the judge's personal morality). It will also depend on whether they feel that civil court is an appropriate venue for your grievance. The nice thing about small claims is that it will be the judge asking you questions, rather than your opponent's lawyer - it will not feel nearly as adversarial, and the judge's primary goal will not be to embarrass you.

I really have to agree with Hugo in the strongest of terms: moving on with your life is the best thing you can do! It's hard to predict which clients will actually feel good about going to court (even among those who succeed) - for many, the victory feels empty, far short of the closure or vindication that they were hoping for. When my husband was alive, he tried to sue a blood bank for negligently infecting him with HIV (this was before effective HIV treatments existed) - I supported his right to sue, but would not (and did not) sue myself. For him, it was about the principle (protecting others from similar harm in the future) rather than the money, so he did not feel bad when the suit was statutorily barred (since he felt that his point had been made). The best reason I can think of to sue your ex is if you don't care about the 5K you might get, but want him to learn his lesson so that he will not be so reckless in the future (i.e. to protect his future girlfriends). If this were your point, you could ask ONLY for punitive damages and request that the money be paid to the charity of your choice - perhaps some sort of charity that does research on HSV or provides supportive services to those infected. This would, IMO, have a pretty good chance of success (judges seem to like it when people want their damage awards donated to charity).

But if I were you, I would not be focused on HOW I got herpes. I would be focused on living a happy life with the virus (which is indeed possible! I do not have herpes, but I have been HIV+ for many, many years, and I cannot imagine a happier life). Yes, your dating life may be complicated (if you're unwilling to deal with rejection, there are websites to find partners with whatever STD you have; because herpes is so common, you'll have lots of options. But don't just assume that you will be rejected. I have been with an HIV-negative man for the last 8 years, and he is the smartest, funniest, most handsome man I could ever have hoped for! I know many other serodiscordant couples. One positive, one negative CAN work out - opposites attract!) Focusing on your own woes is really not a good use of time, and it will not lead to happiness. IMO, the best way to stop yourself from focusing on your own woes is to give of yourself to others as generously as possible.

[I should note that I do have a JD (law degree), but have not practiced in many years (I went back to grad school and found a career I enjoy more!), so you really should direct all legal questions to a practicing attorney who will research the issue rather than just say what he knows off the top of his head (sorry, but I don't have time to really dig into this subject)]