How do I let go.

I’ve been dating my ex boyfriend for a year and 4 months, we had some rocky parts in our relationship but I was looked in the eyes and told everything would get better, I was promised to have another chance and than I get a text last Tuesday at 4:00 while at work. Paragraphs about breaking up with me, I did everything for our relationship, I paid for everything, drove an hour over to there house at least once a week and every weekend, I gave my heart to them and was crushed. I’m told he loves me still and is sorry to do this to me, he said he loves me multiple times and that I was a good boyfriend and a good person. So why leave me after I’ve done soo much and you still love me. we had promise rings, we were gonna get married someday. I barely had any control in the relationship, it’s my own fault because I barely ever stood up for myself and now it’s like this. He blames it on me when he has the issues, bad mental health, is bi polar, has DID, and is taking testosterone as well as bad trauma. All things that make his mental health not good a lot of the time and yet it’s my fault. He has boundary issues, mainly with sexual things which is totally fine until it became worse and worse. At the end point of our relationship I couldn’t even kiss or cuddle him because it made him uncomfortable because I had a boner, like I’m sorry I can’t control something like that, it just got worse and worse where he became stricter and stricter with anything sexual related and even non sexual, I couldn’t be my energetic self, I couldn’t be on top of him just in his small bed without saying I’m overwhelming him when he finally wakes up at 2pm, he never worked, and never tried to improve his life very much. I carried the relationship and always accommodated every new boundary and issue yet I’m here heart broken and destroyed. I can see it’s unhealthy now but I can’t stand that he won’t take any blame for what’s happened. I just need help getting over this. I apologize over and over every time I hurt him because he would be sad and crying, but honestly the things he was hurt by were things in a normal relationship that most people let go of easily but he couldn’t ever. And I tried soo hard to help him yet at the end of the day I’ve been destroyed and thrown away and I want him back but I can’t get that.