I've had a pain in the middle of my chest right below my sternum and it goes into my left ribs. feels like almost a cramp. what could this be?

Chest pain: Short lived but very severe chest pain in a teenager is almost never going to be a heart attack. It is more likely a kind of cramp, muscular pain. You should see your doctor for a proper history and physical exam.

Left chest pain: This pain, if Sharp and fleeting, worse with a deep breath,cough, other motion may be a pinched intercostal nerve which runs between two ribs. It tends to subside on its own. If you have fever, cough, chills, severe chest pain with a deep breath or shortness of breath, or persistent symptoms, you should be examined by a physician. Any appropriate tests will be ordered.