What causes hyperactive lungs? I had the methacholine challenge test and I was very sensitive. How can I fix this naturally? I'm on advair 100 now.

Difficult. Mostly by avoiding those environmental stimulants but desensitization with the aid of an allergist might help.
Asthma. The most common cause in someone your age would be airway inflammation triggered by allergies. Airway hyperactivity is a component of asthma. The advair you are on is indicated for asthma. I would suggest you see a board-certified allergy/asthma specialist for an evaluation.