I went for a run yesterday (for the first time in years) I went a little too hard too fast and quickly began to lose my breath. I sat down, trying to catch my breath but it only got worse. It was to the point where I could barely breathe. My chest felt tight, I was wheezing, my stomach hurt. It was scary. I almost took myself to the er. It took about an hour for me to recover. To be fair, I do have anxiety and I quit smoking about a week ago. Today I feel better but still have a shortness of breath here and there and my chest feels a little tight. What could be the cause of this?