It sounds to me like thus far your mainstream experience has been one of guesswork, but that is often the case. Not that advice on a public forum site won't also be guesswork, but I do know a thing or two about asthma (quite the family history, including my grandmother, son and cousin) and perhaps I can hlep.
First of all, though it would seem counter-intuitive to inhale smoke when you have asthma, smoking herbal mullein leaf will often provide almost instant relief. Mullein is a long-time native remedy and the plant has both anti-spasmodic and anti-inflammatory properties. I can absolutley tell you from personal experience with myself, my partner Luella May and my son that it has worked awesomely.
Another thing which has worked wonders is a combination of:
1. Nebulizing with a mixture of five parts quality colloidal silver and one part lobelia extract, and
2. Taking a a couple of capsules of a Chinese herbal formula product called ClearLungs Extra (look it up and check out all the healthy ingredients it has for the lungs).
You can nebulize several times a day as needed, and I would also recommend taking up to a couple of ounces of oral colloidal silver daily to help even further with any mold/fungus/bacteria problems. Note that you can also add one part or so of mullein extract to the nebulizer instead of smoking it (though I think smoking it works best of all).
Just wondering - have you ever used a cup or two of black coffee to help relieve and/or ward off an asthma episode? That was a real life saver for my grandmother several times and it has helped Luella too.
For a bit more information, see the article I wrote for Natural News:
"Use nature instead of dangerous drugs to treat and relieve asthma"
http://www.naturalnews.com/030235_asthma_natural_remedies.html
I hope that helps. I know that asthma and restricted breathing can truly be a beeyotch!
Make sure your blood pressure levels are normal/sodium levels are high enough. Sometimes low blood pressure can cause constriction.
Rubbing some essential oils on your chest might help a little-eucylaptus oil/peppermint oil or
Taking a bath with vaporizing oils-i would get a shower filter and limit your chlorine exposure.Chlrorinated showers can be constricting. If you take a hot bath make sure the water has no chlorine.
Interesting-so nystatin helped you to breathe better? Maybe fungal infection in the lungs due to mold exposure?
Experiment with other anti-fungals to see if it helps with your breathing--coconut oil/undecylenic acid etc...
I know people with breathing problems have used sudafed and have helped. But thats only a quick fix and will exhaust the adrenals.
Avoid foods that cause constriction/astringent qualities--Avoid caffeine etccc Avoid Diurectics or foods that are strong diurectics=causes imbalance of sodium/magnesium(electrolytes) which can cause constriction.
Hope you feel better---