I've had a lot of intestinal problems which began 3 years ago, my doctor diagnosed me with irritable bowel syndrome because I would get diarrhea, constant nausea and overall sick feeling, and a really horrible pain in the lower right quadrant of my abdomen. Eating too much, or certain foods, would leave me curled up in pain and I went to the hospital a few times. The pressure would cause a lot of bloating and it would hurt all the way down to when I pass a bowel movement. Doctors always focused on my ovaries and nothing resulted from that.
The pain in my abdomen is rare nowadays. It only gets bad when I eat too much. I completely changed eating habits and take the probiotics and I think that may have helped with the intestinal problems.
Probiotics are a good start, but you need to feed the flora as well with fibers. Rice bran or oat bran are especially good since they are soft fibers, do not cause bloating like psylllium does and they provide a lot of B vitamins that also benefit the nervous system.
By the way IBS does result from a lack of intestinal flora, so you are on the right track.
Testing for herpes is done through an antibody tests and antibody tests are a notoriously inaccurate. These same types of tests are used in testing for other viruses as well including hepatitis viruses and HIV, but they have an extremely high false positive rate. Being that you never had an outbreak chances are that your first test was a false positive, which again is very common with these tests.
As for the vulvar itching, what you are describing does sound like lichen simplex. There are various things that can contribute to this including allergies, soaps, perfumes, douches, lubricants, condoms, etc. Pantyhose and tight underwear should also be avoided.
If you have allergies you need to focus on building up your adrenals since allergies stem from adrenal dysfunction:
http://curezone.org/forums/fm.asp?i=1527351#i
Building up the adrenals will also allow your body to generate its own steroids to help keep the inflammation down and to help with coping with stress.
Something else that may help is the amino acid glycine. Glycine is both a neuritransmitter inhibitor, which will help calm you and will also reduce nerve sensations causing the itching feeling. Recommended dose is 500-1000mg 3 times daily at least 30 minutes before meals. Glycine is also a component of collagen, so it helps to heal the tissues.
Do not use douches, perfumed toilet paper, salt baths, bubble baths, creams, lotions, etc. that may contact the area. And try not to scratch the area, which will only make it worse.
If you do suspect an infection the best way to address it is to take some probiotic powder, add just enough water to make a thick liquid. Then lay on you back and use an eye dropper to squirt the probiotic liquid in to the vagina. Lay there for a few minutes for the liquid to disperse and absorb before standing up so it does not run back out. The probiotics will restore your good flora that produce mild acids, peroxides and bacteriocides that kill pathogens and will compete for food and space with Candida and other microbes.