no longer turned on sometimes?

My boyfriend and I have been dating for 8 mos now. I know that doesn't seem like a long time, but we've been living together the whole time and I'm certain he's the one for me. I'm 18 and he's 20. I had sex with one other person a few times and it never felt good just hurt I guess I can't remember it feeling good.. he has had sex with a lot of other girls and said he gave them orgasms. When my boyfriend and I first started having sex it was unbelievable.. it was so great and we did it all the time. It felt good anywhere he touched me and especially my breasts. Anyways since then we've started to get really discouraged because I can't orgasm. He doesn't think he's any good and it's causing problems. I can tell it bothers him. Sometimes I don't want to try because im afraid I won't finish. when we were having sex a few times he got me to where I think I was about to orgasm and I was like paralzyed and collapsed. Was that an orgasm? I wanted to figure it out so I finally tried masturbating and used a vibrator only on clit. After a while I had the paralyzed feeling again but nothing more. Any suggestions? I feel like after I realized I couldn't orgasm I wasn't as turned on anymore and I don't get as wet as I used to. It doesn't even feel as good when he sucks my nipples which used to really get me going. And as soon as I start feeling good I wonder if on gonna finish and it ruins it. I really just.want to finish with my boyfriend. He means so much to me.