I've been having on and off burning for the last 4 years. Randomly, I'll go to pee, and the burning will start. The burning only lasts maybe 15 minutes and happens about once every two weeks or more. But it feels almost exactly like a UTI. When I was young, I had many, many UTI's, and they eventually did a cystoscopy. I haven't had one since then. But I've went to the doctor a few times in the past 4 years and they said the tests always came back negative. I know its not an STD because I was still a virgin when it started. Any ideas?