"She "forgot" to tell me that she was positive for genital Herpes."

Herpes is not something you "forget" 4 months after becoming infected.  Especially when taking a daily Valtrex pill as a daily reminder.

"The doctor at the clinic said that i shouldn't worry about anything, She had never seen readings that low."

Your doctor is an idiot, but this is typical doctor talk.  She should know that Herpes takes 3-4 months to show up on a blood test.  She should also know that low test result readings are irrelevant - test results are either positive or negative, not more or less positive/negative.  You can use the negative HSV readings to determine that you likely did not have HSV 3-4 months ago.  Test again in 3-4 months.  If you test positive then you can narrow down who gave it to you given the time frames.  Also find out what type of test you had - IgG?  IgM?  Herpeselect?  Western Blot?  Some tests are notoriously inaccurate but some clinics still use them. 

"She had unprotected sex with her ex-bf many times since her diagnosis and he never contracted it from her."

How does she know if she gave her ex herpes if he can't even know?  Remember the time frame - she had contact with him "many times" since she got infected 4 months ago, and early contact is more likely to spread the virus since the body has not developed antibodoes to suppress the virus.  Did he even get tested?  Do you really trust her to tell you the truth after she "forgot" to tell you that she had a highly contagious virus?  And yes I said highly contagious.  One contact with her possibly gave you Herpes, and she had many contacts with her ex.  Do the math. 

Now you have the duty to abstain from any contact that could infect someone else, for the next 3-4 months until you get tested again, and then you get to have "the talk" about you having Herpes, and/or asking ahead of time if your future partners have Herpes.  Some people don't really care that they have Herpes -  to them Herpes is just the price to pay for having a promiscuous lifestyle and not caring about infecting others.  I guess Herpes is not so bad for those who are careless, carefree, use sex to identify themselves, and don't worry about their mental or physical health. 

Your lady friend will likely infect many others during her lifetime, and your doctor will continue to enable the spread of a permanent contagious life-altering disease by telling you and other patients to be care-free about the disease, to not worry about it or tell others that might get infected.  Methinks your lady friend got the same advice from her doctor that you did, which is why you may now have Herpes.  Of course the doctor told her all of this while writing out a pharmaceutical prescription that she will likely be paying for for life, and a bill that goes to support the doctor's giving out irresponsible advice to others.  See how that all works?  Do the math.  

Be your own man, do the right thing no matter what a doctor tells you.