Bf turn offs...

My boyfriend is an awesome person and our sex is great but he wants it way too much. To the point where I stop enjoying it and it gets annoying and I have to say no and he gets annoyed with me in return. He's into "rape" fantasies and I am actually into that sometimes but not when I don't feel like having sex anymore. It becomes a turn off. I've tried telling him he wants sex too much and he has a higher sex drive than me but he just says "I'll get you use to it" like... Wtf no it doesn't work like that. It's affecting the relationship. So idk help.