I'd get to a cardiologist and PC doc ASAP. Hard to say what it is but a racing heart in the manner you described sounds similar to a tacycardia. Mine used to happen just as you decribed. Better to be safe than sorry. Tachycardias and arrhythmias are common and very scary. I'm learning to live with mine. It's not easy but I'm managing. Best of luck.
If you're fainting this should be investigated fully to make sure it's not heart related. They can do a tilt table test to see if they can find the cause and rule out certain things such as heart related, ANS (autonomic nervous system) sometimes even infections, ear problems and a multitude of other things can cause fainting with or without symptoms.
In the meantime, try to find any triggers like physical or emotional, dehydration, standing sitting etc and please be very careful - fainting can be very dangerous...I've fainted driving and recently hit my head on the side of my tiled tub and had a concussion, contusion and severely sprained my neck.
I'm just a patient w/a healthy heart other than Atrial fibrillation so I"m not going to venture a guess as to what your problem is.
The fact that what is occurring includes your passing out for a few minutes is valid reason to mention this to your doctor. Don't let him just pass it off as you are too young to have any cardiac issues.
Do I think it is something you have to be seriously worried or scared about? No. But I do think the passing out along w/the other symptoms warrants investigation by medical professionals? Most definitely.