Skin hurts. Shingles? Getting worse. Help?

Im 15 years old and first, about 5 days ago, my back started hurting..more precisely on the left side under my shoulder, exactly where the bra strip goes over. Then my skin under my left breast started to hurt, exactly where the wire of my bra goes along..and now its starting on the left side. At the beginning i thought it wasnt anything bad. But now every move i make, it hurt soooo badly. The thing is, there is no rash, nothing..the skin looks perfectly normal, but its hurts like its paper ripping or burning. Does anyone know what it could be? Is there a possibility of having breast cancer? Or shingles?