Sex help !!

My boyfriend says he loves to have sex. I love to have sex and I try to have sex with him often and he turns me down always with an excuse of some sort like I need to get this done or I'm tired. I don't know why he won't fuck me he only wants it when HE wants it. Yes I talked to him about it and he says if we didn't argue he'd be in the mood which isn't true because I've tried when we didn't argue and his idea of arguing is me telling him that I want him to have sex with me. Help please I feel so ugly and unwanted