Your doctor and your research are correct, COPD is irreversible and progressive. In my case however the first doctor was an asshat who when told I smoked and was having extreme trouble breathing, decided that I had late stage ii, early stage iii COPD without proper testing.
When his treatments seemed only to make things worse, despite my having quit smoking cigs (still smoke weed now though i quit at the time) I sought a specialist, Dr. Yongyudh Ploysongsang at Bumrungrad, who spent maybe 30 minutes listening poking and prodding me. He decided that I likely had pneumonia and before recommending any other tests or treatment gave me a course of antibiotics.
My lungs cleared in days. Spirometry numbers reverted to normal. On my next visit I was told the COPD diagnosis was at best premature. I got lucky.
But I had to live with the thought that I did have COPD for months before getting the reprieve. In the end it worked out. nothing else could have got me off of cigarettes.
Dr Yongyudh Ploysongsang -- I highly recommend him and a number of people here, (including Cheryl) told me to look him up.
He has decades worth of US certifications, and none of the god complex many Thai doctors seem to display. Although it cost me 3000 thb for the first consultation, he was worth every penny and I will continue to check in with him