I am new to Reddit, but have seen some amazing feedback and hope somehow hearing back from someone will bring me some, if any level of peace. 
I've been in a relationship for over 3 years. He's been my first genuinely nice guy, extremely patient and sweet, a relationship I only used to dream of. For a borderline, you can only imagine how that manifests within me. 

Around two years in, the insecurities, projection, control and 'manipulation' caught up with him. He stopped being intimate with me. (I am a victim of sexual assault as a child and sex has become a huge factor of validation for me, as has physical appeal.) We werent intimate for a year and a half. It made everything that much worse. Then the raging began. I'd never experienced something so out of my control before these episodes. I was physically abusive, grabbing anything I could to mutilate myself, screaming, in between bouts of sobbing and crying so hard I was gagging, to screaming at him over why I wasn't worthy of love. Things got really really bad, and we broke up. The month we were broken up was a living hell for me. He'd moved on to another girl (a week later) and I relapsed on pills, stopped eating altogether and lost 15 lbs. I would text him every day not realizing he had me blocked and wouldn't receive anything I sent. A couple weeks later, I call him and it goes through. There's a strange sense of calm inside me and I apologize for everything I was and did, he agrees to see me and work on it again. Big mistake? 

It's been a month since we've been back together. The girl he'd been seeing had left him for her ex, but they'd still slept together that whole time. The pain is agonizing. Thinking about her with him, him touching her the way I needed him to for so long, but my own abuse and emotional downfall made me undesirable. I can't handle it. It has been eating me alive. We still haven't been intimate. I still can't have one day I don't flip out about how much it hurts. How betrayed I feel. How worthless. I can't even get my own boyfriend to make love to me. I am in complete and utter agony. It gets so bad, he has become physically violent back because he can't deal with the rage. He can't deal with being hit anymore and he ends up hurting me way worse because of his physical size and strength. I end up with scratches bruises and cuts from either myself or him. Sometimes the dog gets involved and I've had an instance where she broke skin from biting me during an episode. 

I love him so much. He has done so much for me and I know the mistakes he made were a result of mine. He has always been there and been patient and kind until I start projecting and needing him to make me feel valuable, worth loving and cared about. I hate, HATE knowing he fucked another girl just because she was nicer than me. He even told me if he could just have my body and her personality it'd be perfect. 

I don't know what to do. I had to call out of work today because I couldn't stop the rage. I want help I want support I want something that will show me I'm not a terrible person, and I do still deserve to be loved. I go back to therapy tomorrow. I'm on mood stabilizers. 
I don't even know how to end this post I just know I'm so close to giving up on myself. I can't seem to find my worth, no matter what I do or tell myself. I am nothing good or beautiful or sweet or nice. I feel like a waste. 