Boyfriend and future MIL

Victoria
I hate the way my boyfriend acts with his mother. His mother is constantly trying to dictate his life by telling him what's better for him and makes me sound as if I am the worst thing for him. She always mentions on how we aren't good together and how I'm gonna leave him or cheat on him. They have a very weird relationship it's almost as if she treats him like that's her husband. My boyfriend and I have lived together for two years now and are expecting our first child together. It's rare we associate together ever since she called me a fat whore who will fade with time. I have never done anything but be polite to this woman but it's getting hard not to dislike her more since I'm obviously not going anywhere since I am now having his child. He acts so different when he's around his mother almost as if he loses his voice and seems to be more distant with me whenever she is around. She is staying at our house for the week and wants to make monthly trips when the baby arrives. I don't know what to do anymore. It's not that I don't love my boyfriend it's just I cannot stand his mother.