What could be causing trouble breathing? i feel it in my upper airway, like it is swollen. the symptom comes and goes on its own. no other symptoms.

It is best to see: Your doctor. It seems you have had pft to determine if you have lung problem and i suppose that is normal. What seems to be happening is you tighten you throat or upper trachea. It is not swollen actually as it comes and goes, swelling does not do that, tightening does. It may even be vocal cord dysfunction, but unclear. Wait for you doctor to do all tests and diagnosis. Good luck.