"It's almost like he is embarrassed by being sexual."
Well, if you have any interest in trying it, my guess is that he'd probably be into being called a bad dirty little boy, tied up, made to play with his penis, spanked, blindfolded, and in general dominated by a woman who tells him exactly what to do, holds him down, and climbs on top for a rough ride, slapping him if he protests, and then comforting, praising, and reasurring him like a child after he climaxes.
Of course he has fantasies. He is too ashamed of them to share them. Asking him what he wants in this case is probably about as effective as a husband asking his wife if she fakes orgasms if she's been doing so for years. Neither is going to reveal their authentic sexual selves.
So, I figure you can give up or you can try playing out some really dirty fantasies (without asking really, though of course without genuine force).
