My husband gets angry when he’s told no

My husband is in the navy. So he’s in and out from being home. In the last 6 months, I have made it a point to improve our sex lives. He’s always ready for sex. I went through a period after having our third child (when our middle child was just 16 months old) of not being in the mood. I was determined to change that. I’ve made it a point to say “yes” as much as I can and to even initiate sexual intimacy. We were having sex everyday that he’s home sometimes 3 times a day. However, there ARE times when I’m just not in the mood and I feel I’m within my rights to say “no” and have him respect that. Usually it’s because the kids are sick, or I am sick...something. It never matters what the “excuse” is. He gets pissed. Last night I had told him no because it was 1am, I just got done with some homework (I’m a full time student), and I had been running on 4 hours of sleep from the previous night. I was so tired my head hurt. So I just explained to him why I wasn’t feeling it. I thought he had accepted it. But once we got up to our bedroom, he stood there waiting. And when I didn’t start doing anything to prepare to have sex he said “are we really not having sex?” To which I replied “no, I just told you I didn’t want to”. He got angry. He stormed off to sleep in another room, but discovered the guest bed wasn’t made and came back to our room and called me a cunt before laying down and going to sleep. I’m so sick of him not ever understanding why I just SOMETIMES don’t want to have sex. I’m never allowed to say no without being made to feel like I’m a piece of shit. I don’t know what to do about it.