Why does my mother keep treating me this way?

I can't tell you why your mum acts like this. Only she can. I think that you two should pick a day that you both can take off together and maybe have a little spa day together, either at home or a professional place and you should have some mother-daughter bonding time together and let her know how you feel and try to come to an agreement that will work for both of you. If that doesn't work, then I guess you'll have to wait till you can move out, but, even after you've moved out, try to maintain a good relationship with your mum. You never know, you might have a better relationship with you mum living away from her than you do living with her.