What Is This? Bad Heart Pains/etc.

Alright, here's the problem. Sometimes i'll just be doing something, doesn't matter what it is, sitting and watchign t.V., exercising, walking, cooking, anything and this happens at random times. All of a sudden my heart area gets the most horrible horrible pain imaginable. I've been standing up before and it'l happen and i'll jsut fall over, it hurtas too bad to do anything buit cry and twist and turn. I'll also get shortness of breath. It feels like something is building up in a spot and about to burst whatever it's building up in cause it can't get past where it needs to.

It'll make me horribly dizzy, also. It just feels like somethign is stretchign way too far in my heart and the pain is just horrible, I can't explain it. I've had my whole forehead cut all the way across, i've been hit by a car, tons of things. Nothing even comes close to 1/10 the pain of this. At the end of whatever it is (usually after about 2-3 minutes) it feels like something popped and whatever was building up started just flowing away.

My family does have a history of heart problems, not many family members but some. I'm only 15 and don't feel like gettign a heart attack or anything similiar soon. So, any ideas as to what this is?