Can't cum....

My boyfriend and I just had sex a little while ago and we were just laying down, cuddling, and he was kind of out of breath. I asked if he was doing okay, and he said yes, asked if I was doing okay and I said I was fine. All of the sudden, his mood changes and was like "You didn't get off, did you?"(thinking to myself Well no.... usually I'm out of breath too honey, but I didn't say that) But when I said, no and that's okay(which it should be okay...I think), he got all weird about it and said no it's not. I don't get off like I use to. Is there a reason behind that? Is there something I can do to help me get off? I feel like it's me that's having the issue, not really him... :/ I enjoy the sex we have, no matter the length, but it's almost like the big moments we do have it, he never thinks I enjoyed it even though I do...