The staging of COPD is mostly for docs to help them determine an appropriate treatment plan for you. What stage you are doesn't define your COPD necessarily and it certainly doesn't define you as a person. It really doesn't matter what stage you are; what's important is what you can do and how comfortable you are doing it.

When diagnosed I was at 55% (stage 2). I struggled to do anything because of breathlessness.
I've been on PR courses (twice), and learned not to panic when breathing gets hard, breathing techniques and personal confidence.
Now, at 43% (stage 3), I walk and cycle in all weather's. I won't get better BUT I can slow down the speed I get worse at and the stage is just a number - if not I'd be doing less now than I used to ... but I do more!
Too much of life to be lived to worry about COPD slowing me down.
Have a great 2024 (and 2025 when it arrives!)

Your pulmonologist should run tests! Myself I don't think about it I just praise God I am still breathing for Him! I believe there are far worse diseases than this COPD! I love exercising and going to pulmonary rehab! It has helped my breathing