Im 17years old 5'2" and 115lbs , and I have never had any childhood problems, recently I have been short breathed and my heart has real sharp pains. I work out 4 days a week in my weight lifting class at school. And when my heart gets pumping it feels like something is jabbing my in the heart and it hurts to breath. And other times my heart will be fine and I just cant breath very well. Anyone knows what is happening please let me know.