Petrified of my mom

My mother and I have had our differences and as of now we have a rocky relationship. I keep feeling like she is hiding something from me, and I keep having these terrifying dreams that she is going to try to get my baby from me. I know it sounds crazy but if you knew my mother it wouldn't. She is very sneaky and immature and I'm scared that if I mess up once as a mom she will try to get have my son taken from me. I want to stop all contact with her but if I push my mom out of my life she will take my sister with her. Now I feel like I'm torn between my son and the sister I pretty much raised while my mom was busy with her boyfriends.