Cough and Breathing Problem after Cough.

My father is having cough problem since past 10-12 days. Although, medicines are given along with nebulizer and steam. It has resulted into lower cough but whenever he is coughing, he is feeling very much pain in chest and abdominal. After every time he coughs, he is complaining of low breathing and weakness. But after 15-20 minutes, he says that i am. Fine now. We are checking SpO2 level also every 3-4 hours. It is sometimes 88, then 84, then 90, then 85...it revolves around 80-90 evertime. What should we do now, we are not understanding. Should we give him the oxygen concentrator, or should we consult the doctor. Or all this is happening due to cough problem and it will go away with cough. Please suggest what is to be done. I am enclosing his previous prescription too.