“ADVICEE”!!! My boyfriends sisters...

So I’ve been with my boyfriend for almost 2 years. I have a 1 year old daughter that he has pretty much helped me raise, and Im 5 months pregnant with his son now. His 3 older sisters USE to like me in the beginning but after a few months everything went to hell between us. They don’t like how I talk to their little brother when him and I are in a argument and they say I’m TOO crazy for him. They always have something to say about me, They act like he’s the victim. They get even more mad at me when he don’t show up to family events but I’ve never told him he couldn’t go.. I tell him every time that he can go but that me and our daughter will not be attending so then he decides not to go either. I know he wants to go though because he’ll try to convince me to go just for a little bit and I do feel bad about it but I don’t want to associate myself around his sisters if they don’t like me, you can feel the awkwardness and animosity in the air. If I was to go I wouldn’t want him to leave my side or to even talk with his sisters because I feel like it’s disrespectful to me because they don’t even speak to me, i feel left out, like they want me to be the outcasts but I can’t ask him to do that because that’s his family. They’ll hate me even more. I know my son will be their nephew and they expect to be in his life and to see him but I don’t want them in my sons life if they have no respect for me or my relationship with their brother. Am I over reacting? Am I in the wrong? I’ve tried to start conversation with one of them over messenger to at least break the ice, knowing that she’ll tell the other sisters I tried to reach out but I never got a response. He wants to go to his family’s for Christmas dinner and his sisters will for sure be there so I really don’t want to go but what should I do? I love this man and want him to be happy but i hate the anxiety and the uncomfortableness I get when I’m there.😒