What would you do...

So my boyfriend and I have been together for awhile. We used to have sex all the time everyday sometimes up to 3 times a day. Once I got pregnant it slowed down to once a month if I was lucky and the last 3 months of my pregnancy we didn't have sex at all. I would ask why he said he didn't want to harm the baby. (I know men think that) well I found out he had cheated and he swore he wouldn't do it again.. I figured things would go back to normal after the baby was born. Our son is almost 1 now and we still have sex maybe once every 3-4 weeks. I try to initiate sex all the time and he just turns me down. We have the conversation why he don't want to have sex and it turns into a fight because he gets defensive he says he don't need it everyday and he's too tired or its to late. Then again the only time we have sex is when I bring this conversation up. I'm tired of it I don't need to have sex every day either but a few times a week would be nice. Idk what else to do. I don't want to fight with him every time I want to have sex but every time I bring it up he gets mad... Any advice would be appreciated...