I’m mad at myself

So my bf and I have been together for a significant amount of time and we regularly have sex. And every single time we do it, he does everything for me. And in turn I try to reciprocate the favor. Except he doesn’t cum. AT ALL. No matter how hard I try, no matter ow perfect my “O” is, no matter how long i do it for, he never cums. Instead he just flips me over, and fucks me from behind. And recently I apologized for not being able to make him cum and he said it’s okay, but I know its not. Now I don’t know what to do. How do I make him cum/ how do I do better in general?