Have you been using anything you shouldn't have been? Diet pills, drugs?
It could have been an anxiety
attack. I had one a few weeks ago and literally thought I was dying (I'm only 20 and in great health). It was scary as $h!t. I had similar symptoms to yours.
The only way to know for sure is to go to the emergency room. They can run tests to check your heartbeat (EKG), give you a chest x-ray), and run other tests to determine if you've had a heart attack
and if so, what the damage is. They'll also run blood tests to check for blood clots
and heart disease
. It's best to get it checked out ASAP because it could be causing further damage. A regular doctor's office does not have all the equipment to do all this. They can do an x-ray, blood work, and an EKG at best.
*If you think you're having/have had a heart attack, it's not a bad idea to wake up your parents and tell them.
Feel better! =)