I don't enjoy sex

I know most people are going to think I'm crazy, but I've had multiple partners in life and have always liked the idea of sex, but when it comes down to it, I never really enjoy it. It's been that way with every partner. I get in the mood but then it's just like, blah. I have also never had an orgasm (again I know you all will think I'm crazy lol) but is this normal...? I've been with my fiancé almost 4 years and we really want a baby, but it's hard when I don't like sex that much..and I don't want it to feel like a chore. Any ideas? Anyone else struggle with this?