What are the possible causes of severe cough, cold, clogged ears, and wheezing sounds?

Hi doctor,

As a night shift security guard, I sometimes have duties in a closed building with air conditioning (AC) running. However, I am preparing for an upcoming physical test and have been running every night in the cold rooms of the building. Unfortunately, this has caused me to develop severe symptoms including phlegm, coughing, stuffy nose, clogged ears, and wheezing sounds from my lungs. I have been trying to alleviate these symptoms by taking antihistamines and using steam inhalation, but they have had no effect. As a result, I went to the clinic doctor provided by my security company for treatment. The doctor diagnosed me with exercise-induced asthma and prescribed inhalers and other medications, but they have not helped either. I am still convinced that my symptoms are caused by an infection, possibly from food, cockroaches, or even COVID-19. I have been dealing with these symptoms for six months now and need help identifying the true cause and finding appropriate treatment. I had a full body checkup at the hospital, which included a chest x-ray, but they did not find anything wrong. I still believe it could be an infection and am seeking guidance on appropriate medications.

Please advise.