I don't think there's any pill for fatigue. I would see your doc. While fatigue is often a symptom of COPD, it's also a symptom of many other things, some fairly benign, but others pretty deadly. You need to see if you and your doc can't figure out the cause of your fatigue and develop techniques for you to deal with it. If it does turn out to be COPD, chances are good that part of the problem is depression. There are two things you should talk about: beginning a regular daily exercise program and some counseling to help you deal with depression.
Besides what Jean has mentioned, it appears most of us no longer have a regulated lifestyle like when we were working or active. Our body clock changes depending on our current activity level and also the amount of energy needed, to keep our heart over working,to cope with the drop in lung function.
This can cause periods of extreme tiredness during the day light hours which we compensate with a few naps.....When the ''Normal'' night resting period arrives, we usually are still wide awake or find much shorter actual sleep is needed. So for me I can function pretty well on 3-5 hours per night/early morning....