Hard to say. I went through my dating craze in 7th and 8th grade, and even though all the girls I dated called each other boyfriend and girlfriends, I'd never really say we were in a relationship. That tally alone probably adds up to about 6 or 7.
But in reality, I'd say definitely one, maybe two. Hell, the farthest sexually I've ever gotten with a girl wasn't even while we were dating.
So yeah, the first one was with a girl in my sophomore year of High School. We were dating, and all the while we were good friends. The relationship progressed pretty far, and we generally got closer as it moved on. It didn't end on the best of terms, and we don't really talk to each other any more after a series of confrontations that weren't exactly my fault, but could have easily been avoided if I had manned up.
The second one was... a long story. Basically I was a good friend to her while she dated two guys in a row before me, and in the end I eventually was somewhat of a rebound when her previous boyfriend had cheated on her. Funny thing was, I had previously expressed my dissaprovement in said guy, so when it happened I was there with open arms. We got pretty close, got a little intimate, and than she got cold feet, and over the course of a few freak outs which we were both responsible for, we stopped talking to each other, and currently hate each other's guts. She's currently dating said guy who cheated on her again.
Once again, the problems weren't really my faults, but easily could have been avoided if I had just manned up. So, needless to say, I've learned from my failures.
Edit: Anyways, the moral of the story is no matter how much you think the person is acting unfair, or unjust, try as hard as you can to put on a smile and deal with it. It will save you a lot of heart ache and pointless anger.