I am twelve years of age and since i can remember i have been getting sharp shooting pain in my chest (left-side, however a pulling pain in the right side of my chest but that is only during exercise.) , in which my mother believed to be nothing, around june of last year i visted my doctor and he did not detect anything to be wrong, recently the pain has become more frequant and more painfull. i am also getting migrains to the left side of my head and the same pain at the top of the left side of my stomache and the left side of my torso. what could this be