My boyfriend will not have sex with me!

Please, help! I am at my whits end. My boyfriend is 33 and I am 26. We met each other through our work and we were both going through a divorce at the time. He has no children and I have one from my previous marriage. My current boyfriend and I reside together in a home he has purchased on land contract. 
Now on to the issue at hand...
He REFUSES to have sex with me. He always says no and that he is tired or isn't in the mood. I've told him that it makes me feel like he doesn't care about me anymore. I've told him that I am young and have a healthy sex drive and nothing helps.
I also find myself having sexual fantasies about other men in around and I feel guilty. Idk what to do!!