Welcome to HealthcareMagic forum.
Thanks for providing complete and detailed account of your problem. After going through the details, the close possibility which I think could be responsible for your symptoms is "hyperventilation
Hyperventilation syndrome is a condition where an individual responds abnormally to an anxious state. The increased and fast breathing induces metabolic changes result in subsequent symptoms such as tightness of chest, difficulty to breathe and so on.
Though treating anxiety
is most important, the episodes can be treated by breathing into a closed airbag.
Let me assure you, that this condition is not associated with any lung or heart pathology.
I suggest you to try breathing into a bag the next time you get this episode and let us know if you feel any difference.
Thanks again and regards