I had this happen to me on Sunday and it felt like a heart attack with stabbing sharp pain at my sternum radiating up and out to both sides, at one time feeling though it went all the way through to my back. I did not feel any thing broken off anywhere. It hurt much worse as I tried to take a bigger breath. An ambulance was called for me and I was admitted to the hospital. A lung CT and a heart cath was performed to rule out my heart. I have RA and fibromyalgia and this turned out to be a worsening of those diseases, specifically Costchondritis. My Dr told me that stress and fatigue add to it and that it should be better in a week or so, but that it can reoccur and become chronic. I am already taking 9 anti inflammatory prescriptions so no more were prescribed. I hope this helps you.