I hit my bf and he says he will match that

We are in love. We have it all, passion and lust and playfulness. He is the one. We've been together for 4 years and met each other's families numerous times and he even bought me a ring. But he comes from a home where he witnessed his dad hurting his mom. They are immigrants from Italy and it is more common there. He abhors his dad's behaviour and has never ever been abusive to me. But, sometimes when I'm upset I take out my frustrations by waking him. He asks me not to and says it's wrong. But today we were arguing and I hit him again and he gave me a big smack back and said if I keep hitting him he will do it back to me... How do I stop this before it gets worse? I truly don't believe that he will ever hurt me but he's trying to show me that it's wrong and how would I like it. Maybe subconsciously I want to know if he would ever hurt me like he saw his mom...