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This sounds like a very unstable and upsetting situation. I would strongly encourage you to get some professional help for yourself, if not also for your mother. Finding a psychologist to talk to about how to cope with your day to day life with your mother, how to manage your feelings about it, how to find a way out of this situation, and how best to take care of yourself seems like it could benefit you a lot right now. It really sounds like you could use the extra support.
I would also suggest that you try your best to get your mother involved with a psychiatrist as soon as possible. I hear what you're saying about former doctors not being all that helpful and your mother being rude to them, but it really sounds like your mother's illness is taking over and making both her and you miserable. There are doctors and medications that can really help and I would strongly encourage you to try again. You can always take your mother to a local crisis center or emergency room- they will figure out how best to help her from there. That way, it does not become your responsibility to get your mother care.
It is very important that you take care of yourself right now. You have been working so hard to take care of your mother- and this is beyond your control and ability- she really needs a professional- and in the meantime, you have been neglecting yourself. Please get some further support from a psychologist and/or a friend, a family member, a support group, a church, etc.