Thanks for the comments so far.
I guess I also should have mentioned that, since the first shortness of breath episode that occurred, I have not yet had any difficulty breathing. Taking deep breaths is not a problem.
I also probably should have added that strenuous activity does not seem to make any problems worse. That is to say, stairs don't bother me, going for walks don't bother me, and having sex is one of the few times I feel rather well (instincts taking over?).
I have tried to lower my stress level in any way I can. I have not yet taken up regular exercise mostly because I hate gyms and I hate the cold. Thus the winter months plus my job in computer software lead to a fairly sedentary lifestyle until things warm up again
Also, at times the pain would be evident in my back and particularly in the muscle area where the breast meets the armpit (can you tell I am quite savvy at anatomy?). After taking up some stretching, that has mainly gone away, although it doesn't seem to help the root chest pain.