Okay, you're going to think that I am just kidding around when I say this but I'm not:

Use force. Rape him. SHOW him that he can like it. Tie him to the bed or cuff him in his sleep. But show him how his body can respond to different kinds of stimuli than just him pounding into you. Ya gotta be quick though.

Sometimes tough love is the best therapy.

Okay, well everyone has given you every other idea and this is mine....maybe this is silly to you, but in the words of Mr. Bill Cosby "there comes a time of despairation when you'll even give the rediculous a try."