Alastair,
I don't know if you are worrying unnecessarily. I have had COPD after a bout with mycobacterial pneumonia for almost 2 years now. I worry sometimes when I am having a rough day breathing. But if it is not a daily occurrence, I stop worrying about it. COPD is a uncurable disease that is different for every individual. It also is a roller coaster. Good one day, bad the next. All we can hope for is being able to control it as much as possible to keep it's progression at bay. Worrying does not help. Worrying does not affect the outcome of any test and sure doesn't make life any easier for you. All it does is sap energy from you. When I am aware of my own worrying, I do everything I can to distract my attention from it. I work on one of my hobbies, I do Qigong to help me relax, I will watch a movie, clean up around the house, visit my grandsons, to name a few. Easier said than done sometimes but gets easier the more you do it. Let the forum know how everything turns out. Take Care and God Bless.