OP, not to be trite about it, but it sounds like you're suffering from emotional exhaustion (which I recognize because I'm suffering myself). It's not the same thing as being tired, and somehow being able to name it made me feel slighly better.

Maybe this might help?
https://www.betterup.com/blog/emotional-exhaustion

The more you give the more they expect. I’m in the same situation and I’m about to break too. Hugs to you, just writing here helps for a sounding board. Try not to be drawn into her vortex and keep your boundaries. This is the final curtain call for them and it is a very hard transition and realization. Find things that will keep her busy like a good book - maybe take her to the library, a magazine subscription, Netflix. If she is mobile, definitely try to take her where she could meet others. (Maybe schedule a lunch at a nice senior living facility) the more she is distracted, the better for your health. The day is always better than the night (Sundown syndrome), take walks, sit in the park. You are giving unconditional love and respect to your mother and are a wonderful role model. You are a beautiful soul.

This is difficult, OP. You are being a good child. And it is hard and it’s probably difficult to adjust.

Some suggestions.
1. Can you hire someone to help? Even a few days a week? For a few hours?
2. Meal service? So you don’t always have to cook from scratch? Or your mom can make herself?
3. Are you near a local community center? Places like the YMCA or JCC often offer groups and activities for older people to engage and keep them active?

OP, do you have any relief? My father moved in with me when his health failing. Ultimately, hospice was brought in and the first thing they asked me about was, “Who is relieving you?” I said I could manage it all and they insisted. Hospice’s POV was if you get the flu and are in bed for a week, you NEED relief. My siblings stepped up and each came a weekend day to relive me. It enabled me to go to the grocery store, spend time with my kids or simply, read a book. It was life saving for me. You are doing a good thing and are a loving family member.