conflict at home

  I don't know what to do anymore. Me and my bf have lived with my parents for almost two years. It was fine at first but then my step dad left my mom and she started acting a bit crazy you can say. I love my mom and want to be here for her but she's becoming a handful and I feel like her mom. Which made it horrible for me because I had to pick up the slack financially and physically. My brothers who also live here are no help and make the house dirty and gross and hardly help with bills. My mom forces my bf to do shit instead of asking my brothers. My boyfriend has had enough, He's angry being here and I understand. And he vocalizes it but then my mom acts up listening into our conversations.  We were making moves to leave until we found out we were pregnant. And financially it would be smarter to stay and help us out a lot but the living conditions are getting worse. All we ask is no smoking weed in the house but my younger brother (22 years old) doesn't listen and my mom lets him get away with murder. It's gotten to the point my bf wants to beat him up because he's tired of his shit. I wanna leave but my boyfriend who is now not speaking to anyone thinks we should stay until the baby is here. I'm unhappy and have serious anxiety being here dealing with everyone bitching about each other. I try to stay quiet but I can feel it effecting my relationship now on both ends. Im forever the monkey in the middle .... some advice pleae :(