I'm pissed off that my boyfriend is going to visit his mom.
Why are you mad that your boyfriend is visiting his mom?
I don't want to be at home alone.
I understand that you might be scared to be alone while he is gone, but you cannot get mad at him for visiting his family. Did you ask if you could go with him, so you are not alone?
No, I haven't. I don't want to impose.
Family is important to most people. You should be happy that he cares about his mother. Any fear you have can be eased if you just talk to him.