I've actually been debating starting a new thread (to get more replies) or if I should post my issue here, because quite frankly I'm in a nearly identical situation.
I could almost copy paste parts of the OP

haha.
I'm 20, I've only had sex with two partners, the first being my highschool love, we both were virgins, etc. The second ended up being a one night stand / fling. I think she was looking for casual sex, and I'm just a relationship only kind of guy and scared her off... I feel really weird contacting her after the fact to ask if she had any STD's, because I know she wasn't a virgin... I knew her fairly well beforehand, and so I have some trust in her, but since she sort of fell out of my life after that, I'm a little nervous, because my urethra started hurting a month or so after, it's been about 2 months, going on three and the pains that were here have pretty much gone away.
I guess, I know I should go get checked out, but I don't know if I should be getting checked out for a UTI, or an STD of some sort, or something entirely unrelated like kidney stones or something -_- I'm pretty much just entirely nervous about going to the doctor for all this, especially now that it's subsiding, but I also don't want to be a safety risk for future relationships... argh. I guess I'm just looking for some input as to what my deal might be, and some moral support, heh. It's hard to talk to the people close to me about it, even though I know they wouldn't turn their backs on me.
Heh, Ohiokid, if only we could go get tested at the same time

(For moral support, nothing weird intended by that statement, haha ><)