Is my boyfriend acting weird?

I've always thought that sex with him was amazing and that we've always been good about taking turns and paying equal attention to each other's needs. This past time though he went down on me almost every time we had sex and would hardly let me return the favor. I love going down on him (like really. I truly enjoy it) so I usually do it a lot. This time he kept telling me no though and kept going at me and trying really hard to please me. I know this sounds weird I'm not complaining per se. At first I thought he was just trying to be nice but then I started getting suspicious that he didn't like something that I was doing and didn't want to tell me. Or that he really just wasn't enjoying how sex felt with me at all and so he made it all about me every time we had it. 

I'm all for getting all the attention every once in a while but not if it's because he's not enjoying it. I want to drive him just as crazy!

I don't know if I'm being paranoid or what but it seemed a little odd. Maybe he really was just trying to be good to me. I don't know? Any input???