help!?!

My fiancé and I have been together on and off for over 5 years. We used to have sex all the time, even when we were broke up we would hookup like crazy but this last time we broke up was when he went to college for his first semester. Since then I feel like every thing has changed, we are happy and we love each other don't get me wrong. But as far as sex is concerend, it's rare, and he doesn't even get into it like he used to. I've tried everything I can think of but I just don't know what changed or what to do.