Is he cheating?

Ok I need help I'm at a loss... My child's father and I have been together 5 years he's cheated previously but I thought we had moved past all that. Now I'm suspicious we haven't. My son is 1 1/2 years old. We both work opposite shifts of 12+hours a day. We haven't had sex since before Halloween. I try to initiate sex but he always turns me down. When I ask if something is wrong with me he says he's not going to have sex with me because I'm begging for it?! Really?! Wtf!!! I've tried to dress up or do things he likes to put him in the mood but I'm still met with stone cold rejection. He barely texts me trough the day anymore keeps his phone on airplane mode when he's at home saying it "saves the battery" when I get a different response besides me begging for it its he's too tired we work separate shifts and as soon as I get home what used to be our time together has turned into the time he hops up and goes to the gym with his friends!! Am I crazy or does this seem fishy?