Im a 13 year old average weight and height boy. I dont eat alot of bad foods and today at reces we were playing red butt which is a game where you throw a ball at a wall and run and touch the wall if you fumble, not too tiring. I caught the ball and threw it, then all the sudden my heart started racing REALLY fast. Other people felt my heart and they didnt know what was wrong, but one person said her dad was going into A Fib when that happened. That has happened before if im just sitting on the couch and run up stairs, but not that fast and for that long. Can anyone tell me what is wrong? I dont have any heart problemss or i think my docter would tell me. Thank you