Chalupa, I too haven't found out what's causing my shortness of breath. Did you know that some medications cause these breathing problems? GERD does, too. So does hiatal hernia. Ditto for certain kidney diseases, vocal cord disorders, asthma (which I supposedly also have) and cardiological issues. Acid getting into the lungs will cause breathing problems also. Any of these causes of shortness of breath, or a combination, could be the reason for mine. Can you walk up the stairs if you take it easy? I can do it once, but not twice in a row. If I forget and go too fast, I get out of breath.
What is costochondritis? Sounds like some type of inflammation.