Hey, Imma girl so i hope you don't mind me replying....
Aywys, this one time, i was chewing ice breakers gum rite before I gave oral sex & I guess the coolness or something from the gum make him finish faster. He even asked me what I had been chewing. He also said it felt better then usual too. So you could try that.
Also, Idk if you already do this, but when your giving oral sex dnt just use your mouth, use your hands too. Like use your mouth for a few minutes, then use your hand for a few minutes, then go back to your mouth. Do that ova and ova. (if he likes this) This should also help your jaw so it won't hurt so bad.
Hope I was some help! Good luck!