3 Year Old Suffering From Frequent And Severe Wheezing

My 3 year old daughter had been suffering from frequent wheezing for past 2 years. She has been on Montair course for 2 months then the medication shifted gradually to Seroflo 125 (1 puff twice a day) to Maxiflo 125 (1 puff twice a day) to the present Maxiflo 250 (1 puff twice a day). However, the inhalers do not seem to be having any effect on her condition. We are giving her Inhaler through spacer and baby mask for 1 minute each time. She is currently also on Asthafen syrup and L Montus (1 tab. a day). She had Pneumonia 2 months back and was hospitalized for a week. She had wheezing last month in which we gave her Levolin nebulization 3- 4 times a day in conjunction with the routine Maxiflo inhaler. This continued for 15 days. After around 5 days of stopping the nebulization, she started wheezing again. This time, Levolin did not help and she was wheezing even after 5 days of inhaler and nebulization. She was then given a 5 day course of oral steroids (Omnacortil). Wheezing appeared to have cleared after those 5 days but started just 2 days after the oral steroids were stopped from being given to her. She has been wheezing for last 1 week + and Levolin nebulization again did not help her out for 1st 5 days. Hence, the doctor suggested Duolin nebulization for another 5 days. Today is the 2nd day of Duolin (= Maxiflo+ Asthafen+ L Montus) and she is still wheezing. Please advise what else can be done. Just FYI- we got her Comprehensive Allergy Panel Test done a week back and the test results did not find any allergen. The result was negative. Please help...as our child is not really in a good physical health for last 2 years continuously and it is very upsetting to see her in such a bad shape