Orgasm?

I really don't post anything but I really want to know something about orgasms. I've never had one so I can't tell if what I felt was one, I think it was but it was not an intense feeling as I thought they would be. My boyfriend and I have been sexualy active for some time and I never had an orgasm before, I actually thought I couldn't reach one. In the last 2 time we been together I felt a sensation where it felt really good that I wanted to stop but at the same time to keep going it happen 2 times that day but the second one was less intense you could say. would that be consider like a small orgasm? it also only happens when I'm on top of him and I really can't tell if his hitting a spot inside me or if its my clit rubbing against each other I need some info about this since I really don't have anything to go with since his been the first guy I been with. Thanks