Rubies, you could be me a couple of months ago.
My (now ex) boyfriend has longstanding depression, anxiety disorder and OCD. He tried to control me constantly, because loving me made him feel even more insecure. If I didn't reply to text within five minutes, I'd start receiving snarky messages implying I didn't care about him. If I wanted to do something on my own - for example, Christmas shopping for DD when she was staying at her dads - it would be sign that I was utterly selfish, cold and didn't love him. If I wanted to go for a walk with friends, invited him, and he didn't want to come, he would spend the whole time I was out sending me messages and then spending the evening being vile and accusing me of God knows what. Sometimes, even my facial expressions were wrong - I should have looked happier to be with him as we were walking down the street or something equally mundane. This escalated to the point where every evening we spent together, he would at best be criticising me for being aloof, cold, distant and a snob, or at worst, yelling at me because I didn't love him enough. The final straw came a couple of weeks ago when he didn't like the fact that I spoke to an old friend and shared an joke with them. This resulted in him screaming, crying, flouncing, slamming doors and stalking off into the night. I told him a couple of days later that I wouldn't forgive his behaviour any longer, because to do so would be to condone it, and he was becoming so out of control I didn't know what he would do next.
He was holding me responsible for his mental health, just the way your boyfriend is, and you are not responsible, not at all. The problem is, because these men think we can "save" them, the fact that we aren't / can't / won't makes it ten times worse.
You'd be doing both of you a favour to let this one go.
I have the greatest sympathy for anyone suffering from mental health problems - hell, I've suffered a few myself in the past - but there is no substitue for professional and medical support.