Breathing probelms. , what is solution ?

Some times I feel I have to take deep breaths in order to satisfy my lungs, i have to take yawning to satisfy breaths , I also feels sometimes its empty in my chest and there are unsatisfying breaths, How ever PFT - NORMAL XRAY- NORMAL CT SCAN- NORMAL ECG- NORMAL SPO2- 98 its happening with me since 5 years On and off, once it happens it takes months to go and no medicine Montair LC , abphylline , Doxolin helps me I am smoking on and off since 6 years There is no cough , no wheezing , No runny nose, No sneezing, No snoring I am able to do exercise in gym , I am able to do running for 1-2 kms , weightlifting, Cardio, I take walk for 1 hour Still I feel something in chest is missing and breaths are not satisfying and I have to take deep breaths to satisfy lungs What is this problem known as , what is solution ? Height - 171cm Weight- 76 kg