Should I move in with my fiance?

‘m 19 almost 20, second year college student. First off, I go to school about 30-45 minutes away from home and I’ll probably have to commute since I can’t afford to live in a big city. I’ve commuted before using our family car, but my twin sister is going back to school too at a closer community college and my mom said she’d have the car. My fiance lives about an 8-10 minute drive to my school. Second, things at home aren’t great. My sister has a mega problem with me and I don’t know why and is yelling at me and, resorting to violence, (I don’t fight back) has even punched me a few times today, once in the back of the head and now I have a mega headache, and has said she doesn’t want me here anymore. I’m going to look at a studio near my school tomorrow, but it may not work out. My fiance has told me to move in with him to save money and all (but he lives with his mom…who is loud and VERY honest, and a party-er.). Should I? I’m really close to calling his mom and asking her. My mom is taking my sister’s side and really doesn’t care about mine. What should I do?