HELP.. my man acts like he doesn't want sex

So I recently got married and now that we're married, my man can act like he doesn't want to have sex. He's my first love (although i'm not his first), and so I'm not sure if that is the reason why but I always feel like I'm initiating sex, and he never is. I want it to come from him more often so what should I do? Should I just pipe down and stop mentioning it until he acts like he wants it? He works full time as well as is in a Physical Therapy program full time so he's always exhausted, but I just feel like there's never any "us" time.