I am also 20 too, and I know what you are talking about. I think what you're talking about is palpatations, which are caused by stress
. It actually does sound like you're having panic attacks...it's okay, I do have panic disorder, but with medication and cognitive behavior therapy, you can get through it.
But first get in to see a cardiologist just to make sure your heart is healthy. If they can't find something wrong, please keep your mind open to the possibility of panic disorder.