Mark
That feeling that you are getting, happens to me all the time. My lung collapsed last year, and they used a tube to re-inflate it. I recovered, but never fully. Every time I do exercise or get stressed, I get that same pain that you are describing. The doctor told me the exact same thing, that they can't do anything about it. I'm guessing that the pain is due to the muscles around the lung. Since the lung never fully collapses when I get that pain, it must not be a pneumothorax, just very similar symptoms.