I'm sorry to hear that, you have my sympathy. I definitely agree with what others have said about having a doctor who is both knowledgeable and supportive of your desire to keep backpacking. It also seems from what I have read that there are effective treatments for COPD and that staying physically active is good for it, as well as for your morale.
I have been having some respiratory issues myself. I guess they ruled out COPD, probably more like bad allergies along with some asthma. Whatever, it seems like there are a lot of grey areas between conditions and multiple possible diagnosis, so I'd be sure to get a second opinion, your doctor could be wrong, as well as be defeatist.
They attribute a lot of COPD (and other respiratory problems) to smoking, which I have never done. However, I know that for me, smoke from wildfires and campfires is a major aggravating thing (as well as pollution and damn dusts at my job). Avoiding campfires and smokey campgrounds is a good thing to do, if we have breathing issues, and I'm tying to plan backpacks that stay away from wildfire smoke, difficult though that may be.
Thanks for sharing and keep us posted. As you can see, many of us share many sorts of ailments in common, and it's inspiring to hear how others are coping and still pursuing our common passion.