I’m fucking over it!

I’m 23 years old. I have been sole caregiver to my mother since I was 18 when my step father left and never came home because he was sick of carrying her. She’s entitled. Rude. She thinks that if she needs to go somewhere I just need to drop everything and go or let her drive when legally she’s not allowed to drive due to seizures. I’m at my wits end. She wasn’t exactly a great mother growing up, she was never home, she was a workaholic, she got married to a man that hated me and my sister and didn’t divorce him until he got arrested for stealing money from his job.(like 500,000) and just in general didn’t spend time with me and my older sister. Regardless over the last couple of months she’s gotten 10xs worse. She refuses to clean. She doesn’t want to watch my son even for three hours while my fiancé and I work. (When my son is asleep or may be awake for an hour of that time) she is disabled and she does have genuine issues I get that. I don’t ask for much. Sweep the floor. Wash her dishes. Pick up after her dogs and cats. Today she text me and said she needed flea medicine and didn’t I want to take her. I was trying to nap because I hurt my back a couple of weeks ago and I can’t sleep well anymore. My fiancé saw the message and said he was going anyway he would get flea medicine for her but he didn’t want her to come because she doesn’t like him and she’s always ridiculously rude to him and he would have our son so he didn’t want the issues in front of our son. Anyway when he gets home I realize he got the wrong flea medicine and I laughingly went to my mother to tell her. She yelled and said she needed more things and how stupid my fiancé is. I left. She followed me to my room and knocked asking what I did with the flea meds I told her and closed the door. She waits a minute and opened my door again. I lost it. A little bit of respect is all I ask for. I’m not a child. I pay every single bill in this house with my fiancé. She gets $500 a month in back child support from my bio dad. She never offers to help pay a single bill or anything at all. Don’t come open my door when it’s closed and I’m clearly done with the conversation. I’m not a fighter. I have no desire for confrontation. If I walk away don’t follow. She came in and got loud with me again. I told her to leave my room and she slammed my door while my son is asleep in the room next over. I told her unless she wanted to find somewhere else to live never slam my door again. I DO pay all of her bills and I have no problem supporting myself without her. Kinda feeling guilty for saying that but my GOD I’m TIRED!