If it's atrial fibrillation, which is the most common irregular heartbeat, you can learn more about it here: http://www.StopAfib.org
You'll find causes and triggers, risk factors, why it can be a problem, and how it's treated.
While atrial fibrillation isn't as common in younger folks like yourself, those who "over-exercise" can be more vulnerable to it. In addition, it often runs in families, and younger folks who have it may have other family members who have had it.
Mellanie True Hills
Atrial fibrillation survivor & founder of StopAfib.org patient resource