What Can I Do if Im Not 18 and My Mother Is Using Crystalmeth Around My Little Brother?

Well this first started when we got into into an altercation with my mom and she had left and sent me threatening text messages. she had all of a sudden came back and just moved right back in. we had moved all her belongings to the garage and found little baggies that was used for meth and also scraping materials along with a cutting board. she had came back soon after that. I was on the phone and s just walked up to the main monitor and she disconnected it. after i had called her a stupid mother and she struck me in the face. well my little brother was left at my friends house while she was gone. he is scarred to move back with her and feels she doesnt love him any more. i need help and fast because me my fiance and my month old daughter are staying at a friends house and i dont know what to do.