Exhausted, Needs Support

My grandma has had stage 4 lung cancer since May of this year and it is steadily getting worse since a tumor is causing fluid to build up by one lung. 

 

In the beginning my mom promised I wouldn't go through it alone this time because I live with my grandma and was her full time caregiver at one point. Now I've grown older, have somewhat of a life, a boyfriend and dog I'm lucky to see when I have time. But my mom is so bad at staying calm, remembering medications, and being patient that my grandma still heavily relies on me.

 

Both my mom and boyfriend are not physically around enough to really help me take care of her. I'll come home exhausted from work and still have to cook for her or some project and she wants everything to be very clean all the time. I often run a ton of errands and then she tells me to take back food or items she doesn't want that I bought. I can't have the dog over anymore because it sheds too much and my boyfriend's family doesn't like him out when they have to watch the dog. So I have to go to him to spend time with him. My mom tells me to take more hours at work, claiming she "has it covered" when I'm scheduled to take my grandma to an appointment. But I can't trust her. 

 

My boyfriend just told me he won't be joining us for Thanksgiving and I was really looking forward to the support. I have to pack up my grandma and take her to my mom's, then pack her up and bring her home as soon as she's worn out. It's depressing for me and I really wanted the support of him joining us, even if he wasn't helping. It hurt much more than I thought it would for him to say he couldn't make it. 

 

How do I ask for more physical support so people will come to me instead of having to take care of them? Covering for my mom and doing things alone really brings down my mental health.