What is his reasoning for not wanting you to go down on him? Maybe if you figure out what he’s REALLY worried about then you guys can fix the problem.
I’d also try to push the envelope a little bit with him in bed. Just test the waters to see how he reacts when you get a little rough. If you want to go hard, get on top and fuck him senseless. Show him that it doesn’t hurt you and how good it can be. Don’t go too far though and make him uncomfortable, just try something a little outside the norm and see if he’s okay with it.
So talk and try to take the lead a bit.