Back problems from boobs

So im 13 with a size C and i've been getting terrible stinging back pain for almost a month. It's painful only on a little area on my upper left back it sometimes feels like somebody is scratching a sunburn. I get pain when standing and basically when my back isn't against something to help support it (back of chair) a week ago it hurt laying on my back. My mother said if I get more constant back pain for a longer time we can she about going to a doctor and doing something about it. Is there any tips you can share, exercises or anything.