A confused teen? I don't think this is fair to me?

Long story short: My parents fight all the time because my dad is an alcoholic. My sister Paige is addicted to drugs and she left our house. Paige stole from my mom, me, and my brother. My brother and I are only 11 months apart. (He's soon to be 16, I'm soon to be 15) Today, my mom, brother, and I just got come from a week vacation from NC. We found out from neighbors that Paige was staying at our house for that week w/ my dad. My brother recently got his tonsils out in April and we had some left over medicine/painkillers. (The liquid kind) My mom had marked how much was left and now there is a significant amount missing. So my mom confronted my dad and started screaming at him. My dad was trying to get a word in, but she wouldn't let him. I hate it when she does this. Now I'm sitting in my room crying my eyes out b/c I don't know what to do. I want to leave but I'm afraid that if I leave, my dad will. Please someone tell me what to do?!