Oh OP, so sorry to hear how you feel about things and I wish I could help but I am not very experienced at all in things like this. I do kind of relate to what you are saying but only in a small way. I have in the past at low points looked at a cemetery and thought how restful it must be, but have known that, having dcs, that was not an option. I have also felt at times they would be better off without me but now I am well again, I totally do not feel that way any longer. It is like having two selves. Both are real but the one I am now is a lot easer to be.
I really hope and hope again that you can find your way out of this.
I was lucky and found the right counsellor, who used CBT and some post-traumatic counselling techniques, and drugs, and a lot of exercise, and I did come out of it but it had not been with me for long. I can remember the pain though, and it sounds as though yours is a lot worse and has been with you for a lot longer.
Please give the services you can get hold of a try and try looking for others if they are not improving things for you. It is not just one illness that needs the same treatment for everyone, it can take a long time to find the right way for yourself. Others might have more specific suggestions. Everyone on here will be really hoping you find it soon.
I really wish you the very best, people out here do care.