Advice please

My fiancé never wants to have sex. We used to have sex all the time and now it's like every other week. I have a very high sex drive and I am struggling with this. He says it's because he has no drive and it's noth fault but I have a hard time Believing that. I don't know what to do. I will try to initiate and he gets mad or pushes me away. If it's not his idea it doesn't happen and it's really getting to me in a negative way