My heart sometimes hurts really bad. This has been going on for the past 4-5 years (i am now 16.) The other day I was playing basketball, and I stay active and work out most days so moving around is not a rare occurrence, but my heart started beating insanely fast. I thought I was having a heart attack or that my heart was literally going to explode. It was extremely scary. I have asthma, but my breathing was fine; it was just my heart. I stopped and calmed down for a minute and it went back to normal, but I have been a lot more intensely active before and that has never happened. Could a doctor please answer this? It scares me that I may have a heart problem. When it first started back when I was 11-12, my mom took me to the doctor twice and they just said a muscle around my heart was growing, but they never did any tests and I never thought they were right about it but my mom belived them. Now at 16 and done growing, it still happens. Do any doctors know what this could be?