Lucky you! You have a condition with a "million dollar title" (great for dinner parties!) but nothing much to really worry about. I had it too, and when the doctor told me, he had a smile on his face the size of Texas...! Seriously, it just means that the cartilage in your ribcage (your sternum) is inflamed and sore. Feels an awful lot like a heart attack, but your heart is probably just FINE. The pain goes away if you don't strain yourself. In the meantime, you have a lovely condition with an incredible name that you can drop at parties and at the office water cooler and people will think you have something really dreadful!