I read your previous few posts on the STD web site and had an experience not too dissimilar from yours. I started running about a year ago, and had symptoms similar to what you described; the fact that I'd been with two girlfriends over that summer made me nervous enough to go see the dermatologist. It had been 54 days since the last encounter when the symptoms appeared. The doctor said it definitely wasn't herpes or any other std, just some irritation from either sweating (from running) and masturbation. Shaving "down there" apparently makes it much more likely you'll see symptoms like this. I tested negative for herpes. So don't worry, this is normal.