My boyfriend is TERRIBLE at going down on me!?

okay, hes not the worst when he just starts out. he does a great job of turning me on but he'll start to aggressively use his fingers and TEETH and i have to pretend to just so he'll stop. the thing is he LOVES to go down on me so its not something i can just avoid. he wants to do it all the time. i don't know how to tell him though. or what to tell him. im seriously moaning and screaming out of pain but he thinks its because he's so good, and then he thinks i come so it just makes him want to do it even more the next time. WHAT DO I DO?????? oh and breaking up with him isn't an option, im terribly in love with him this just sucks!