My bfs baby mama is driving me nuts!

So three weeks ago my bfs baby mama (let's call her Alyssa) moved out from living with her boyfriend. That's when she stopped calling or making an attempt to see her daughter. This past weekend, by gets a text from Alyssas mom about why he wasn't answering Alyssas calls. He never responded so the next day I messaged Alyssa to ask why she lied and it was clear she just had no interest in her child. To which she told me to mind my business. And then started telling me about happy vibes and pregnancy and how once again to mind my own business. Well it is my business when her 4 year old daughter acts out because she can't see her mom and I have to deal with temper tantrums. So it takes her 3 days but she finally messages my bf saying they need to talk and that I have no right to message her. I have two kids of my own, so I was trying to get across that maybe her daughter needed her. When she messaged my bf, he loses his shit on me saying that I have no right to message her. I've been more of a mother figure to his little girl than she's been in the last 2.5 years I've known him. Doesn't have anything to say to her about lying but then I read the texts between them and it seemed like she would say things and he would just agree. All night last night all I heard was " I really need to call Alyssa". So I told him today since they're so great together I was going to move out because she's always right and I'm always wrong. When he broke his phone because she sparked an argument between me and herself on his phone, I got blamed for him breaking the phone not because of her comment that he cheated on me. And once again I'm wrong because I messaged her because of his kid. I'm just always wrong. He's told me off so many times but never a ill word to Alyssa. He treats her like a saint and like I'm always the bad one. I can't take it. I hate him so much right now and want nothing to do with him. What do I do?