What would cause a sudden, piercing pain in the chest, by the heart?

Sometimes, often when I'm laying on my back falling asleep, it hurts like hell to inhale air into my lungs because of this quick, piercing pain that feels like its at my heart, almost as though its being punctured by a needle. These painful occurrences happen rarely, couple nights every few months. It doesn't last long, about 4-5 seconds. I just have to stop inhaling air for a second. The last time it happened a couple of weeks ago, I tried to inhale more air at the same time and it became increasingly painful. What can you make of this? I'm a 17 y/o boy so its couldn't be very serious right? Any ideas are much appreciated.