Breathlessness for last 2 months. Long?

17 year old male patient with PMH of Asthma and CTEPH on riociguat. Gradually progressive tiredness with low grade temp 99F for last 2 months associated with increasing shortness of breath on exertion and dry cough. Had severe pneumonia 4 months back requiring HFNC for 21 days. Shortness of breath and cough increased severely over last 15 days. SpO2 at rest 94% dropping to 78% during walking 20 steps. Last chest xray shows right lower lobe ground glass opacities but no causative organism detected. Blood reports are WNL. Chest findings are bilateral scattered rhonchi on expiration and lower zone crackles. Not responding to nebulizer. Recieved short course steroid prednisolone for 10 days with minimal improvement. SYMPTOMS INCREASED ON STOPPING STEROIDS. Patient is not willing to do HRCT (Thorax) due to risk of radiation exposure as multiple HRCT has been done in lifetime. Can it be due to IDIOPATHIC INTERSTITIAL PNEUMONIA/ COP? IS IT NECESSARY TO CONTINUE STEROIDS? for how long?