Heartbeat In My Stomach For AWhile?

Oookay.. I can feel my heart bbeat in my stomach. Like its at the same rate as my heart. It doesn't hurt at all aand I had it for like 1-2 years. It hasn;t bothered me or stopped me from anything . Im only 12 and I have never had before so it cant be anything wrong like that. I feel fine and normal. But I'm thinking its because im so skinny because I have a really flat stomach and im really thin. So maybe its that? But it's not stopping me from doing anything. I can just feel it.