I know sometimes when my anxiety is really bad I will short of breath. The ekg and chest xray would indicate if there was an abnormality of your heart and lungs. I would say that is very good news. Sometimes I find myself having to take a deep breath and I think like Mark said it's because we hold our breath. I'm not sure why. I wonder if a stressful situation comes on and I hold my breath in anticipation and then realize I'm SOB.