I am having moderate pain in my sternum when I breathe in. Also when I try to lay down I feel as though I m litterally dying. I have had a chest xray, EKG, ECG, Ct Scan, and nothing has come up. I get this pain off and on and it normally goes away with in a couple of days. I have always just dismissed it as an air bubble in my chest or in my back ... however it is very uncomfortable and making my life difficult. Any thoughts on what it might be?