My boyfriend of three years has a history of depression and suicidal feelings, he shared this with me since the beginning of our relationship. 

I love him so much, we even talked about marriage. But sadly I am starting to see how unhealthy and toxic our relationship is. We both are mentally ill (I have borderline personality disorder, anxiety, and depression, and he has major depressive disorder). We both emotionally abuse and control each other. I have finally started therapy/medication and realized it’s been like this our whole relationship for the very first time. 

Sadly, I do not think we can change this. We have tried multiple times and there are signs that we aren’t going to work out in the future. 

He always promised to do therapy and work on himself for me as well, but never did.

He cheated on me in the very beginning (within first four months) and I broke up with him a few months later (once we were a year in to our relationship) because it ruined my self esteem and broke my heart. I ended up dating other men but he told me that he was going to hurt himself and was extremely depressed, after I ended it. 

I spent a lot of time talking to him after our breakup. I realized I really missed him and loved him too much to let him go. We gave it a shot and spent 1.5 more years together. 

I was happy at first, but became even more mentally ill in our relationship. I also believe the same for him. He told me many times that when I left him it worsened his depression, and he would always kind of hint that he wouldn’t be able to live without me, and would kill himself if I left him. 

I truly don’t think this is just for control though considering he told his best friend about it, and the best friend ended up telling me how he heard about that. Also, he has many signs of major depression (not showering for weeks, not cleaning his room, not taking care of himself, talking about how he feels like he’s a waste of space). 

I hate how much pain we cause each other already, but I don’t know what I would do if I was the one to make him do the unthinkable and take his own life. 
I just really want to leave but this is the one thing stopping me.