what do I do with my mom?

ok well im 16 and im the only girl out of 2 boys and since I remember me and my mom always bump heads a lot.Im the one she always yells at and the only one out of my siblings shes ever hit.But when we are not bumping heads we are like best friends we do everything together and get along very well but the littlest things make us mad at each other.Lately I’ve been going to church a lot and I try not to yell at her back but she keeps coming at me.The problem here is I want a mom not her as my friend and I have talked to her several times about it but she never listens.I’ve ran away from home twice before and when I came back she changed for a few days then went back to being the same.So basically I just dont want to live with her anymore because shes never really there for me or my brothers shes always gone to her boyfriends house and he doesnt really let her have anytime with us.I dont get along with him I always argue with him.I would go live with my dad but we dont get along either and he cant afford to take me in.I also dont have relatives around here to go with.What do I do about my mom?shes not going to change,thats a fact and I dont want to live with her either and if I talk to her to send me with some relatives in mexico or wherever she wont let me.The thing with her is that she wants to be out with her boyfriend and she wants me to be at home taking care of my little brother(it doesnt bother me to take care of him)but he is her son though.I have independent studies and im always at home and on weekend I can only go out once and thats it.what do I do??I dont want to be home!