Low sex drive

K.
I'm a newlywed and love my husband, we've been together almost 6 years. About two years into our relationship I completely lost my sex drive. I always enjoy sex when we get going, but I never feel like starting. My husband has completely given up on trying to initiate because I always turn him down. 
I don't think it's an attraction problem, anyone have advice? We only have sex twice a month and I feel like the worst wife!!