babygirl, I am so sorry for your health issues which surely must be compounded by the heartache caused by your mother. My mother is similar to yours and I know all too well how you must be feeling.
I finally came to realize that my mother is toxic and in order to preserve my mental health I must avoid her like the poison she is. Someday your parents will be old and need care. Please refer to this incident when you decline their request for help.