Originally Posted by pocketkangaroo

At your age, it's probably unlikely you have anything serious. Seems like a fast heartbeat and not irregular. Your anxiety toward it probably makes it worse. But still, you should see a doctor soon. Since it only effects you when you workout, they'll probably make you take a stress test. It's pretty easy and they'll at least know for sure. But I would probably stop heavily working out until you've had it looked at.