What to do about messy roommates?

I live in a 3 bedroom apartment with two other girls, Ashlyn and Lexi. When they moved in right after my mom moved out my house was clean. Well now my apartment is gross. I just cleaned my room and all of the mess was their clothes all over from them undressing in my room. Lexi refuses to wash even her own dishes and I have to beg her to clean up any mess she makes. Her mom drops her little sister off here, I have toys bc my little brother comes over, and all his toys will be in his box but when she leaves they will be all over and she wont pick them up. Ashlyn will do dishes but whenever I say a mess is hers or ask her to clean something she goes "no that's not my mess so im not going to clean it." Also Ashlyns has her boyfriend here ALLLLL the time and it makes me uncomfortable. Everytime I say anything about her boyfriend or a mess they made or god forbid if I ask them to clean they call me a b**** behind my back and do nothing anyways. I don't know what to say or do but I seriously feel like a dang maid because I am always cleaning and picking up after other people. Does anyone know what I can do about this?