Oh, Bmee! How rough it is for you. I have a site I loved when my stepmother was ill/dying:

http://caregiver.org/caregiver/jsp/home.jsp

Look at your post you wrote above and maybe journal about it; figure out a "plan" or list of things to do/think for each situation? I would ignore the not-knowing-what-she's-thinking blame and try to "laugh" at it since it's impossible. Make a little joke about how she may have known what you were thinking when you were a child but she's not a child so you don't have the advantage there. Apologize cheerfully that you weren't able to meet her need then, but what would she like right now and you will try to get it for her?

Can you keep track of her appointments? My husband and I have a little calendar just for that, our appointments and he's the keeper but I remind him or check every now and then. Just express an interest every now and then and ask, "When is that so-and-so doctor's appointment again, I've forgotten?" and thus keep it in both of you all's mind?

I remember my stepmother's mother's doctor explaining to my stepmother that it was impossible to stop someone from falling; both because one cannot be "there" all the time and because the "surprise" of the fall, even if one is walking with someone, there's just no way to keep someone upright with only an arm around an arm (although he did teach her how to "correctly" hook her arm around her mother's to provide the most support). Does your mother have/use a walker or cane or anything?

You have to go out sometime; to the food store, etc.; I would make your own schedule and get to the doctor for yourself -- as you have pointed out you cannot take good care if you are not taking care of yourself, if you are so depressed and unsupported! Your health is just as necessary and important as getting food! Maybe you can coordinate your and your mother's appointments so they overlap some? You can talk to her doctors about the problems you are facing caring for her and get their help both with her and maybe for yourself.