I also got severe thrush from an enormous amount of antibiotics from pneumonitis caused by an infection from allergic asthma. The Diflucan works really slow. There is a prescription mouth rinse called Nystatin that you swish around in your mouth for as long as you can, gargle with it and then swallow. It worked for me immediately. You can even use it in conjuction with the Diflucan. I had to ask my Dr. for it specifically. My mom who is an R.N. told me about it-apparently they use it in the hospital all the time for thrush. The Nystatin also stopped the severe burning from the Albuterol and the Brovana. I might also advise you to see an allergist. I found out that I'm severely allergic to several of the chemicals that are in almost all asthma inhalers- I'm glad I saw her first!
It is possible that the AdvairĀ® HFA (fluticasone propionate and salmeterol) Inhalation Aerosol could be acting as an irritant. It sounds like you have Candidiasis, commonly called thrush, of your upper and possibly lower respiratory tract and it is highly likely that it is due to the high dose inhaled and oral steroids. If your pulmonary function tests truly are normal or "even better than normal", you need not be treated with this high dose therapy for hyperreactive airways, diagnosed by the methacholine challenge. Low dose therapy might do the job.
You should have an examination of your throat and larynx, using a fiberoptic laryngoscope. If you have any sign of fungal infection, the steroids should be completely discontinued and non-steroidal therapy given for the alleged asthma. Also, if you do have a fungus in your throat, you will also need antifungal therapy.
My son is on Advair. Did you realize that you must rinse your mouth after using, and do not swallow after dosing? Advair causes thrush if you do not rinse thoroughly after each use. Ask your local pharmacist he will tell you. Good luck!