I managed to get through a bad flu infection in late 2003, but my health steadily declined over the next 5 years to the point where I could not get out of bed t

I managed to get through a bad flu infection in late 2003, but my health steadily declined over the next 5 years to the point where I could not get out of bed two or three days per week. Like, crawling on the floor to get out of bed exhaustion. I've been tested and evaluated for lots of things. Fortunately, not a dire progressive disease like multiple sclerosis or Parkinson's. Unfortunately, I have not been able to substantially improve energy level in a sustained way. There are times when I can gain momentum for about three weeks but then there's a collapse. If I push it, I've had vital signs go awry and it's enough to scare the emergency medical personnel who are called when I pass out... and then a few hours later, nothing worse than severe fatigue. I wonder how far away we might be to sorting it all out, things you shouldn't be doing after a viral infection, or environmental factors that we will discover, or if we will be able to understand this at all without a more fundamental rework of medical understanding.