Chronic Respiratory Problem on Inspiration

I am a 24 year old male in good physical condition with mild allergy induced asthma.

About 2 yrs ago I started having non-asthmatic problems with inspiratory breathing after an episode with a viral infection and possible bronchitis.  I was put on steroids, but they did not help the non-asthmatic problem.  Later I was diagnosed with pertussis, which lasted six months, and giardia, which took 8 courses of antibiotics to remove.  While I was taking the antibiotics for the giardia my breathing inexplicably improved, esp. with quinacrine. However, I still have the same inspiratory problem, of which there is no diagnosis.  I have negative x-rays, CT, and good blood work.  I have good spirometry and breathing tests.  My IGE is 600.   I can take deep breaths and I feel better when walking.  However, I have persistent pain when breathing at a normal rate and some mild interruption during sleep.  I feel like my shallow breathing is being obstructed by something.  I do not experience pain on breathing out.

Could there be any connection between giardia and respiratory improvement? Or, could the antibiotics possibly have improved some other conditions I was experiencing?
What could be causing inspiratory pain/compression in light of negative tests?
What about a fungal infection or autoimmune disease?
Could frequent exercise have exacerbated the problem?
I've seen an infectious disease, allergist, pulmonary, GI, and ENT doctor.  Anything else that could be beneficial?

[National Jewish]

The history you provide suggests that you have relatively mild, generally controlled asthma.  Further that your asthma improved with treatment of the Giardia.  Giardia infection results in inflammation of bowel.  Other inflammatory diseases of the bowel, such as Crohn