I am currently having the same problem, I had a virus about six weeks ago, and have been in pain and had very limited energy since. It is slowly getting better, I now have some days where I feel ok so long as I take it very easy.
The gp said that it is not uncommon for this to last six weeks, or longer, in rare cases up to a year! She said that its normal to have good days followed by bad days. Her advice was, that on a good day, I should only try to do one thing. So that's hoovering OR cooking the tea, OR doing the dishes. Easier said than done when you have kids though.
I'm finding I struggle with my mood on a bad day, the constant pain is draining, and it feels like I will never recover, it has been going on so long. Being stuck indoors a lot, no adult contact from work is also bringing me down.
Sorry, I don't know how useful this is for you, I would say you are probably trying to do too much, if I overdo things, I will definitely have a bad day or two. Pathetically, doing the dishes and hoovering counts as overdoing things right now 
{hugs}