Pulmonary finrosis hypersensitivity pneumonitis not progressed during 1, 5 years on CT but breathlessness and low SPO2 started. Heart been checked, its ok. Can drugs cause it? (micophenolate mofetil)

Likely pulmonary fib. Even though the CT did not show progression, functionally your air exchange may be reducing from scarring and distortion of the lung structure. The most important step would be avoidance of the agent causing the problem in the first place.