.I really try and i want to do it for him but then everything that comes out of my mouth is just stupid and awkward

How does he react? Does he appreciate the efforts, make no comment, or laugh at them? (I hope he doesn't laugh.)

I think your feeling is common and not just with sex talk. It's a feeling of being vulnerable and exposed (and I don't mean naked). I felt foolish doing the karate yell (kiai) when I first started because I wasn't used to doing it and felt that it drew attention (and possible mockery) to me. But the other students in the class were doing and experiencing the same thing and I soon overcame my embarrassment and it became a natural part of the action.

My suggestion? Start slowly, key off his reactions, and don't force it. Talk about it afterwards and get his thoughts on what you said.