Is he not interested in me?

I've been w my boyfriend over 3 years now. We have sex about once a week, sometimes 2 times but that's rare. I want sex 3 or 4 times a week but he just never seems in the mood when I try to have sex. It almost makes me feel like he's not interested in me, but if I say something to him he blows me off and tells me I'm being crazy.. What do y'all think?! I'm 20 and he's 22.