Tracy, I don't know if you use Mestinon? Because it can trigger asthmatic problems.
I always was an allergic person, but never asthmatic (although I couldn't breath when I had anafylaxic reactions of course). Since I started mestinon I got asthma as an extra Dx.
They figured it out because they already suspected it (mestinon + allergies), and ventolin and other inhalers helped me a lot.

Maybe you can ask for a test of your lungfunction, combined with the use of ventolin?

For me asthma problems cause problems with in- and exhaling, it feels totally different from MG causes weak diaphragm. The first one feels more like it's something in the lungs that just won't go, sometimes slimy or irritating, like when you've got the flu. Sometimes combined with pain or caughing.
MG diaphram weakness is (for me) being out of breath all the time, troubles breathing in, lying flat makes me sleepy in a creepy way and gives me headache (both caused by CO2 getting too high), and fysically it feels much lower, I really feel it is not in the lungs, it's a bit lower. It feels like it's too tight to inhale. I don't know if this is helpfull, but sure hope it is.