I totally know what you mean. One store that I've always found super cute clothing that actually fits is
If you can afford it, look up sites like Aeropostale or H&M. Even Forever 21 if you want. If you look up cute clothes for juniors you might find your size.
Hi! I'm 18, and I weigh about 95 pounds. I actually don't have any problem finding clothes that fit me. American eagle has great jeans and bottoms for smaller girls and their shirts fit me really well if they are xs. Forever 21 has shirts that fit smaller girls too. Basically any store for "juniors" will fit you and have stuff that is professional as well.