Accusing me of cheating

My husband is constantly accusing me of cheating on a weekly basis. I have never cheated on him nor given him a reason to think that. It's come to a point where out of rage I told him "yeah, I cheated on you and enjoyed it!" I've had thoughts of cheating on him on purpose to be spiteful. Shit, I don't do anything at all and still get accused, might as well do it and give him a reason. Well after he said that he started denying our daughter who looked just like him when she was an infant.

It all started during my pregnancy when his family started putting ideas in his head. He and his family made my pregnancy a living hell. He denied my baby back then too. He ended up apogizing on his knees for that but he did it again. Since my pregnancy he's been accusing me nonstop. I've gave it a lot of thought and have started to think he's that one cheating on me or why else would he constantly accuse me...