My mom makes me wear clothes I don't like?

I buy most of my own clothes, at least I try to. My mom has to approve of everything I buy, except I really don't like her taste in style. She doesn't let me buy anything I like, she likes t-shirts and flared jeans and I can't buy anything remotely tight. I appreciate her helping me and buying me some clothes, but every time I say I don't like some of the clothes she chooses or try to get something I like, she goes on about how unflattering "tight" clothing is, or how she doesn't like tied shirts or how my chest is too big to wear anything. She hurts my feelings by saying I look unflattering or unattractive in a lot of things I try to wear. I'm 15 and i want to be anle to wear what i want sometimes! I don't try to wear crazy tight skinny jeans or belly shirts or anything like that, I just want to wear normal clothes, like at Khol's or American Eagle. She won't let me wear normal shorts st all, they have to be baggy and at least 2 sizes too big so I can "grow into them." I try to negotiate, like she picks out something, I pick out something, but she won't have it! I'm starting high school tomorrow and I want to feel good in my clothes. What should I do? Thank you!