Why doesn't he get it

So my boyfriend wants to have sex and my back is really killing me because I have a pinched nerve. He won't let up and I could say no I just feel bad. Thing is we are in his sisters bed next to his other sisters room and there's no doors on the door ways just sheets for privacy. He breathes too loud and the bed makes noise and I fucking can't stand it. So I ask him to go down stairs with me and there's like only a couch in this empty room but at least there's a fucking door? I want him on top because I'm IN PAIN remember that and he does so shitty and says "it's because I'm tired and I have to be on top" 
He is really good in bed and that sex was shot so I know that's bullshit. At this point he's pissed me off, I'm not in the mood and I'm in pain. And on top of that I feel like a let down because I feel like it was MY fault that the sex was so bad. He makes me feel like it's my fault. I just want to cry. I just said "I'm done" and put my clothes on and walked off and went back upstairs. Then I tried texting him asking him if he was just going to sleep down there and his phone is in this room with me. I feel like he wants every single thing to go his way. I always have to be on top even when I am in pain and it's like he doesn't even care.