Hon, you need to see your doctor. At 220 lbs and you're only 15 that's just not healthy. At that weight you are at risk for Heart Disease
. So I'm not surprised that you are having these symptoms. I'm sorry that you're scared, but this fear should get you to your doctor, pronto. It's also possible that you have a condition called Chostocondritis. If you push on your chest or anywhere that is painful and the pressure increases with pain then it may be just that and Chostocondritis isn't fatal nor serious. With this you just take an antiinflammatory medication like Advil
But like I said please see your doctor and let him examine and diagnose what's going on with your body.