Rewind to where he didn't allow you to finish your shower.
We don't know what he'd done that day, presumably he didn't need to keep washing up?
But we don't know. We only heard how stressed you were. What had his day been like? Why didn't he allow you that?
It sounds like you're both very stubborn and at an impasse, before things got physical.
Even being hit, he should not have turned on you, being physically much stronger.
What you did was wrong but a man should not hit a woman back, ever, because of the strength-mismatch. This is not to excuse your behaviour. It was very poor.
However, you can't get beyond this. He was unable to give you a shower. He was unable to stop himself from hitting you back. A real man would not have done that. He would have ended the relationship there and then.
You sound like a toxic mix. I'm sorry OP but you need to break up.