My (M19) ex girlfriend (18) has severe depression, which combined with a lotta things and incompatibilities led to our breakup. I still however think she deserves the world, since all the shitty things she (maybe, because maybe Im just an asshole for thinking its shitty) did are due to her inability to control her feelings.

For context, we are still living together since we are (maybe she more than me) financially and emotionally depend on each other. The break up was and is tough, we see each other everyday, and try to act like good friends who happen to live together. It doesnt work that well tho. We get in fights because of a lotta things, and they tend to escalate. Usually its her screaming hurtful things and me occasionally loosing control and getting loud for a little. If I do that she says shes scared of me which is why it rarely happens. When it gets worse, she bangs her head against something, which kills me to see, and screaming that she wants to die. In these situations I either try to talk it out honestly, which never really works, or just give up and try to comfort her back to a place where we can act normally around each other.

Today that didnt work tho. We were playing a videogame and her controls didnt work. She got very angry what caught me offguard because I just desperately want to have a good time with her. I trued to help, it got worked out, but she was already just as angry at something else that couldnt be solved. She felt like nobody cares about her and ignores her on purpose, because her mother didnt pick up the phone when she tried to ask her for a bandage because we ran out and her toe is injured. 
After being caught off guard and put in a situation where I neither want to tell her something she interprets as saying shes overreacting nor want to take her side as I dont agree I disassociated a bit. Didnt say a word and waited till she calms down. In that situation, because maybe undiagnosed adhd I instinctively pulled out my phone. Which I agree was wrong and hurt her a lot. Especially because she already felt abandoned.

She got reasonably angry, I tried to apologize, not take the hurtful comments personally and asked her what would make her feel better. She stated that I dont show any remorse because I was trying to explain why it happened (couldnt finish but thats not the point). I get that it sounds like I am trying to justify my behavior but what am I supposed to do if she doesnt accept my apology. 

The reason I am writing this right now sitting on the couch, while her mother talks to her is because honestly it helps me not freak out. It got worse, she banged her head even harder than usual, threw her phone after me (first time she did something that could actually hurt me) and kicked a chair in my direction (I dont think with intent of hurting me tho, just letting out frustration on me). For the first time it was impossible to calm her down, which is why I asked her mother for help the first time. 
I really wanna help, or help her get help. But nothing works. Nothing I can do works. Two different antidepressants didnt work, therapy doesnt work, havin a psychiatrist doesnt help. She is currently trying to get into rehab but she got put on a waitlist and I really hope that it would help but something tells me it wont. Im worried about her, I want my own life back but cant leave her alone like that. If this keeps going she cant start her carrier again (shes got into a school shes interested in and starts in a couple months after giving up work about half a year ago), she cant do a household on her own, she cant take care if the two cats we got, she cant stop hating herself nor improve herself.

Im extremely helpless. I cant do shit for the person that was my whole life for the past two years. Im hurting her, partly because I cant act the way she needs it, partly because I feed into her issues by offering to take over with everything she struggles with. Maybe it is because Im a mental mess myself that is just way better at supressing it as long as I care about someone. 

Sorry for the long post and the probably bad spelling and grammar, but typing it out helped me stay calm. If you read this: thank you. Especially because I end up deleting posts like this because I get no reaction. 

Well.. yeah, guess thats it. Bye