David, From reading the first part of your post I have to say that routine std testing is not all that it's supposed to be. In fact, they don't test you for all stds when you go in to be tested. You have to find out which ones they test you for, etc. I know for a fact that you are not automatically being tested for HPV (which causes genital warts). I also know that a person can have HPV and not get any warts (signs or symptoms). For more information about HPV you can read up here:
http://members.cox.net/yoshi2me/_link_s/_link_s.htm . Same thing goes for Herpes. Also, it's going to be hard to pinpoint when you contracted herpes since you have had more than one partner. It's possible to have carried the virus for some time and not known it only to find out now through a flare up that you have it. It's also possible that both you and your girlfriend could have had the virus all along and the friction from sex alone might have triggered a flare up. As far as reinfecting each other ~ you don't have to worry about that at all. Once you get herpes ~ you keep it and it doesn't go back and forth like you might have thought. Valtrex is a very good herpes antiviral medication. If you find that you are experiencing too many flare ups you can consider taking the medication daily to suppress the flare ups. All in all ~ I wish you guys the best. Try and hang in there ~ Angela