haven't had sex in 2 yrs until recently..

I had my daughter 2 yrs ago and never had sex until I got together with my fiance. The first time we did it, I couldn't orgasm and I still can't mostly due to the fact that I get turned off in the middle of sex(I don't know why this happens but I hate it), or that he doesn't last long enough for me to have an orgasm. He used to tell me that he could get me off by fingering me or eating me out or by doing different positions but since we've started having sex he doesn't do anything and all we do is the same position every time. I tell him I want to try different ones and he says we can until we go to have sex and we do the same boring position. has that happened to anyone else after having your first baby to get really horny and to want sex only to have it go away during sex?