Hello, Sometimes when my chest feels at discomfort ,I stretch my body like one usually does in the morning. On stretching , I always hear a popping sound in my chest, like some bone cracking/popping in the middle of my chest. I feel some relief after this stretching.But, sometimes a strange pain persists after the Cracking sound, it doesn't last long though. I have this since 2018...had even got an ECG done...but everything was found to be normal back then.