Lizze - the tosspot you describe in your posts is making ME feel angry and I haven't had the pleasure of meeting the twat!
Trust me, it's not you it's him.
I had a relationship where my ex made me feel insecure, EVERYTHING became an argument between the two of us because simply put, he was jealous and insecure.
Not quite the same situation as yours but he chipped away at my self esteem, he got into the most jealous obscene rages if I dared to as much as have a drink with friends, he didn't like me talking to any member of the opposite sex, you get the gist. And I stood up to him every time. How dare HE pin that shit on ME? Yes he made me angry. He made me lose confidence in myself and my own judgment too but I recall feeling so angry and hurt at him for trying to isolate me.
And you know what? True to form he HATED me more than anything for standing up for myself. So he'd chastise me for 'causing an argument'. He wouldn't apologise for anything. He would give me the silent treatment for days on end, he withdrew from sex as a punishment until I said sorry to him etc.
My point is, that these men can't seem to smell their own bullshit. They try to put a woman down so they have her where they want her. If she is submissive he thinks it's great. But if like me and by the sounds of it you, she has a strong sense of self it drives them crazy because they can never truly 'own' you. So they spin the blame on to you. "It's your fault I'm on a mood, if you hadn't have opened your mouth and said x, this wouldn't have happened", or "If you'd have done this instead, I wouldn't be acting like this". Classic abuser tactics.
It's all bullshit, no man worth his salt should put a woman through hell just to prove a point. But they are blind to it. Because men like this are damaged. I could almost forgive my ex as I knew his ex wife cheated on him and left for someone else. I knew he was insecure. I understood. And I would never have given him anything but loyalty. Unfortunately he tarred all women with the same brush and the abuse started almost straight away when we were dating. The jealousy and the kicking off at me, swearing at me for being with friends instead of him.
I look back and think it's utterly ridiculous now. I know it was all coming from him. I know I couldn't have 'fixed' him nor did I want to. I just wanted to be loved but he was toxic.
What happened with your ex isn't your fault. I wouldn't stand for that shit now, and I would have told him to fuck the fuck off if I were you but that's because I've been through this shit before.
It's not you OP, please don't try and second guess yourself. I'm willing to bet my last quid you would have done anything in your power to have not hurt him. So why would he not do the same for you??
Answer) because he's a spineless asshole.