@ashleyh and @katgts Good morning and welcome to Mayo Connect! First, congratulations on your new marriage @katgts and to you @ashleyh in July. I hope that we aren't looking at a new disease for newly married women, lol! In all seriousness I understand not being able to catch your breath as I am a lung cancer survivor. It can be very frightening to say the least. I am glad of one thing though, both of you have had testing done so a lot of things have been ruled out. It sounds as if you both might have inflamed and narrowing airways of the lungs. But this is just a guess. I'm not a medical professional so I can't diagnose you. After my first lung cancer and exercising for the first time in many years I also felt this.
@ashleyh- Just before you felt like you couldn't breathe what were you doing? And how shortly after you returned home did this begin? Did you do a lot of exercising that you weren't use to, scuba diving, etc? Did your doctors give you any inhalers?
@katgts- It seems as if you might have exercise-induced asthma, or more properly, exercise-induced bronchoconstriction.
Were you given an inhaler to help your breathing?

This link might help as this is only a guess on my part: https://www.mayoclinic.org/diseases-conditions/exercise-induced-asthma/symptoms-causes/syc-20372300
https://wexnermedical.osu.edu/blog/out-of-shape-or-exercise-induced-asthma
Both of you should get back in touch with your doctors and see if they think that you need inhalers. If you did not see a pulmonologist then I suggest you find one and bring your test results with you.

@katgts- If you experience any worsening while flying or when you land please seek medical attention. Inhalers can be a God send!