Hello
Welcome to this forum and I am saddened to read your comments. The advice to contact your GP given earlier is important to consider and act upon. That said there are a few suggestions which might help in the here and now.
1) Lets try and tone down the guilt monster in your thoughts. Try and give yourself some credit. You made a promise to your mum but events became to much and now your mum is where she can get continuous care at the level required. There comes a point where one carer can not deliver all the support required. That is reality not any type of measure of yourself. You gave direct support to your mum for years, allowing her to remain outside of a full time care home environment. Your efforts and sacrifices allowed that to happen. I think perhaps understandably in the moment you now find yourself you have stopped appreciating what you did do for your mum.
2) Be clear in your telephone contact with your mother the illness is speaking not your mum of old. Try to keep that point in mind, although I do not doubt such conversations are very hard.
3) You have given so much have you perhaps forgotten to hold something back for yourself? There is more than one way forward for yourself, please believe that. Do you have any relatives or friends you can speak to? Alternatively contact the Alzheimer’s Society help line. You have value yourself as a person. You have tried your hardest to help your mum, but that cannot come at the cost of you losing sight of yourself as a human being. I do not say this glibly but you need to pause for a moment and just think what you have done for you mother in recent years. You have not failed. Dementia as an illness will just keeps taking. You have reached the point when you must think about yourself. Contacting your GP, a help line, friends and family, none of that is weakness it is accepting they can help you.
It is hard to offer support over a forum like this as all I can do is send words. As earlier said to you please keep posting. most importantly do not judge yourself by how others appear to be doing. No one wishes to be a carer we would much prefer our loved ones were well. We all have different personalities, skills, experiences and tread different roads in terms of the caring we do. Your situation is unique, you are unique. It is time to start appreciating what you have done, what it has cost you emotionally, physically, etc, stop the music of guilt in your head and put yourself first. Please take care and be gentle with yourself.