Please Give Me Some Advice

I really don’t know where to start with this but I’ll try explaining it the best I can. Me, my boyfriend, and my son live with my mom, younger brother, and stepdad. Right now I’m 16, but I’ll be turning 17 in a little over a month, and my boyfriend is 18. My mom’s had a drinking problem for as long as I can remember and it’s affected my life tremendously. Me and her used to fight really bad and it often lead to me leaving. I ended up moving in with my boyfriend for two months the last time we fought. She was drinking less as my pregnancy progressed and my moods were starting to balance out and I was able to deal with my problems better (I have bi-polar disorder). Recently she’s been starting to drink more and more again. Tonight, I tried talking to her about it and to my amazement, I didn’t yell or scream or anything like that. I actually talk to her and tried to explain why her drinking made me upset. However, it didn’t go over like I had hoped it would, and she told me that maybe I should just go stay at my boyfriend’s house. Now, I don’t have a problem with my boyfriend’s family or anything, I just prefer to stay at my house. Now, I don’t think I have a choice except to leave. I just want some suggestions on everyone’s take on me and my boyfriend possibly getting an apartment together. I know we’d be able to pay, and I could legally move out on my own if my mom signs court papers. I just want to know if anyone else has ever gone through anything like this and what they did. Sorry if this seems confusing at all, I’m just having a hard time. Please reply, I could really use some advice and support.