Breakup advice?

Lol I feel kinda lame putting this on here but I'm hopeless at this point. Does anyone have any tips on a breakup...? Or like how to distance yourself from another person and just how to do you? Unfortunately I've forgotten who I am almost completely and I don't feel good anymore. My boyfriend of almost 4 years is turning into this person that I've never known and don't know how to handle. I could go on forever about it but what comes to mind is he always blames me for problems and doesn't take responsibility. He literally tells me to my face that "you hate yourself" and that "you need to treat me better and think of me more" I'm being completely mind fucked and it's sad! I keep going back and I don't know why! We have so much history but today was my breaking point when he was on top of me holding all his weight down on my wrists telling me that he could "beat me"..... But even in that moment I wasn't scared, he could see I wasn't afraid of him. He knows I'm stronger than that and it pains me to see someone try and take that away from me. Please be kind while responding, in a fragile state at the moment and just need some lovely encouraging words from lovely people.