This is a complex question. Chronic Fatigue is devastating. By relieving some of the pain, the narcotic is allowing you to function and therefore have ‘more energy’. Bear in mind “energy’ is a simple word for a complex metabolic process. And yes many with CFS and other chronic pain diseases feel more energetic with a opioid.
The challenge is that all medications are really poisons with a good side effect. Opioids especially. There are limits and dangers to opioids.
What you need is a good, kind and compassionate doctor who will spend time , monitor and guide you. They are tough to find. The current insurance/administrative world discourages that type of care. Most physicians are employed with production quotas. Chronic disease care does not meet the plan.
Good luck. There are better days.