etheltbags1 My heartfelt commiserations! My mother became thus, but unlike you I did not live near enough to get called round all the time. However, I had to stay with her instead, for "holidays" to visit.
My mother had dementia, Alzheimer's type. She was just as you are describing your mother before she became obviously impaired by memory problems. I am not saying your mum has the same. Please go to your Doctor and ask for help. Ask what help you can get for your mother. You can't run yourself into the ground like this.
It is terrifying to think we might become difficult when we are elderly. But there's not much we can do about it if it's due to an illness. I will say, my mother was still herself when she was difficult with Alzheimer's; she was a difficult person all the time I knew her, before she had it.
I really do want you to get some help. One person on her own can't look after another elderly person when they are like this. Perhaps the hospital will give you some advice. There might be leaflets about where to go for help. Also I phoned my mother's Doctor, but I knew what was the matter by then and I had the advantage of being a Neuropsychologist, so recognised the brain symptoms.
If your mother has changed in personality, behaviour, ways, then a check-up is in order. She might have some early signs and this might be why she is so difficult.
Get help please. If you don't know what to say, read your letter above to your doctor - and your mum's doctor!
Hoping you find some lovely people to help you, and that with some of the strain lifted your relationship with your mum might become easier. Lots of love, L 