J.M.
I agree to see a therapist, but I think an important thing to recognize is that you need to do this for you, not for him. You write "I want to make him happy in that way." What about you? Sexual gratification is a good thing. I think he'd like to make you happy in that way too. Just like anything else, hoping to change yourself for someone else is very hard; changing yourself for yourself is much more long lasting.
Good luck.