what's this about?

So me and my boyfriend have been together for almost 5 years. We have lived together for almost 2. When ever he wants sex and I don't want it he gets angry at me saying I never want to have sex. We use to have sex all the time 5 or 6 time a week sometimes twice a day. It has slowed down since I work 2 full time jobs and he still only works 1 part time job. Thing are okay until he wants sex again and I'm tired from working a 20 hr day. Well back to the point when I want sex and he says no I'm fine with it like maybe he is tired but there has been a few time to where iv actually gotten a little upset and he makes me into the bad guy. What is this????