Advice 🙍🏻‍♀️

I’m stuck , my mom just had a baby with a guy i absolutely despise....i told her i can’t stand being around him so once my dad has his own house i might move in with him. She told me she doesn’t want that to happen and she will stop bringing him around me so much. But she hasn’t done that. I feel sad because i feel like she has picked this guy over me and my sister. And i understand she just had a baby but I’ve been feelings like that for nine months...Idk what to do....i feel like she’s always choosing someone else over me. And i don’t want to leave my childhood house but i can’t keep staying here and being so unhappy. I don’t smile or laugh anymore. And every time i do it’s fake. 😕 it’s effecting my school work and i just need advice.