How do I improve sex with my boyfriend?

We've been dating for about a year now. When we first met the sex was AMAZING! Possibly the best I've ever had. Now...it's lackluster at best. I don't want to play the blame game, but I really feel it's mostly his fault. He seems perfectly content with a bj and 5 minutes worth of sex. Here I am pretending to get off just to appease him and yet I'm feeling completely unsatisfied. I've tried to talk to him about it but he gets defensive, or doesn't say anything. I've tried to switch up the positions to hopefully make him last longer, but it doesn't work. The biggest problem is that he can no longer last more than 10 minutes at best. What should I do?