Why doesn't sex feel good?

I've been with my partner since we were 14 and we've only had each other. Ever since we started having sex, I've never really enjoyed it. I want to have sex so bad, and I get so wet, but it doesn't feel good! He always fingers me first and bites my nipples and kisses my neck, which all feels great, but when he slips it in me, I start to fall asleep!! I even make us try different positions but nothing really feels good at all. He just does what he wants till he cums. I asked him to try this new position so he could rub my clit while he was in me and after about a minute he said "this is too much work. Let's try doggy again".... :( how can I fix this?!