Fatigue is a symptom of many different conditions, so I'd recommend that you see a doc to be sure that it's not something you know nothing about. If you assume that it's your lung disease you could be ignoring something you really don't want to ignore.

I will go back to your pulmonologist her doctor and talk to him there should be something they can do

Nothing wrong with giving in to a sleep whenever you can. Often to tired to fight it but after working 50 years I'm entitled so are you. Hope you feel better.