It's funny how sometimes conversations are easier on email, even with your spouse. I think it's the time to formulate responses, and that you can say as much or as little as you like and they don't have body language or tone of voice to judge as well.
I say find some of those sometimes fun/sometimes annoying email/myspace type questionaires that are always floating around and send to him, maybe tweaking it to be a little more oriented to sex/relationship type questions. You both might be surprised by the other's answers.
