I didn't get it for quite a while myself. I have to ask, too, are you sure you're doing it right? Ask him what he doesn't like about it, and what might make it feel better, maybe. Less teeth, different angle, whatever. My first serious bf didn't like it either, until one time he finally (gently) moved my head to a different angle while I was going down on him. Soon enough, he couldn't get enough, lol.
Talk to him! Good luck.
Wyst