Please please help me

So for the past year I’ve been having an on and off fight with my mom about her boyfriend. He’s always made inappropriate comments to me about my body and I never said anything (I’ve known him for 4 years and it’s been happening since) but last year in December he was drunk and he grabbed my boob “on accident” didn’t say anything and walked away. I was terrified I didn’t know what to do so I kept it to myself. I have a boyfriend who I’ve been dating for almost 2 years now and ive known him for 4 years. I trust him with my heart and he’s my best friend so I told him about when I was younger and how I got molested by my babysitters son. So he knew already that I’m very cautious about men and I started opening up to him on how uncomfortable my moms boyfriend makes me so he helped me gain the courage to tell my mom. I did last year around February. It felt like she didn’t believe me she was questioning it saying that he said he never did that and of course I was upset that it felt like she was taking his side. To get her to believe me I told her about when I was younger. She didn’t say much she looked confused and upset and then went back to her room. She later told me that her boyfriend didn’t want me living there bc I made HIM uncomfortable. So she bought a house for my 2 brothers and I to live in and she stayed with him. We’ve had arguments about me moving back in and the first time I told her no bc I was uncomfortable still and she blamed it on my boyfriend. She said he’s a bad influence on me and threatened to move me back to my home town. She ended up leaving t alone but we never got closure. She’s called my boyfriend multiple times drunk saying he’s ruining my family and cursing him out drunk out of her mind. Today I was over at her house, her boyfriend was there bc he lives there. (I don’t live with my mom I live with my brothers) We get into an argument because she starts bringing my boyfriend up in a very rude way and I got angry because she has no reason to hate him so much my boyfriend has tried to meet her so many times and tries to be as nice to her as he can but she always pushes him out. I have built up anger about how I feel like she chose her boyfriend over me so I yell at her. A couple months back she called my boyfriend and said I said all of those things about her bf grabbing my boob for attention and the thing when I was younger was for attention. I never brought it up to her bc I knew she’d blame it on him and cal him but today I lost it and brought it up to her and I asked her why she would say that I started crying when she said bc it’s true and left and walked home. When I got home my boyfriend calls me telling me that my mom was calling him telling him a bunch of rude things threatening to “kick his and his moms ass” so I take action and go back to her house to tell her to stop bc she wasn’t answering her phone. When I get there she’s yelling at me saying I only walked out bc of him and that he’s bad for me and he’s disrespectful, and I ignore it and tell her I left bc she said that I only said what I said for attention. She starts yelling gibberish and making no sense and saying irrelevant things. I tell her how I felt she wasn’t there for me when I told her and how she stayed there when I needed her with me and recently I found out my dad has cancer and she hasn’t been there for me on that much either. She starts crying saying she’s doing the best she can. Then starts yelling at me again about that. I never told my brothers about what happened with my moms boyfriend or about what happened when I was younger, they assumed my mom bought the house bc my older brother got kicked out by my moms boyfriend. I told them today bc everytime I give into my mom and let it go but I’m done with letting her get her way. My oldest brother said my mom is very selfish and chooses men over her kids a lot it happened to him with my dad and happened again with her boyfriend. My other brother said the same thing happened to him with the same person who molested me and said he believed me. Idk what to do. I’m scared that I’ll lose my mom too but with how she’s been acting towards me I don’t want her in my life anymore. But I do at the same time. I’ve already lost my dad I’m scared I’m going to lose her too.