I am/was in a similar situation. Getting better is such an insurmountable thing when you're there. When things have been so bad for so long that they're not just normal but comfortable in a terrible way, just telling a friend about it is extremely difficult to do. Even if you can gather together the will to try to seek out professional help, you probably won't keep it long enough to actually make that far. And, some part of you that you're desperately trying to keep quiet is telling you that if getting help is that easy then you've just wasted your life laying around being helpless and useless and shitty when it could have been better and that's something else weighing down the "kill yourself" side of the scale. You've been accepting it and coping with it for so long that it's the only future you can ever see yourself having.