@Lionheart777 have you looked at pacing? Each day build up a very small increment of exercise?
For example, today you walked to the kitchen and back to your room, then you walked to the bathroom and back.
Tomorrow you could do that twice.
The day after three times.
You don't have to do a lot but steadily increasing each day, or maintaining on a low energy day, or even resetting to the basics of the first day when experiencing a relapse.
Pacing can really be helpful for CFS sufferers.
Also just gentle yoga stretching three times a day. Rotate wrists three times every hour for the first day. Second day rotate wrists and also rotate ankles three times each hour. Or start twice a day to start off with, depending on your level. You know your body best.
I am doing The Alexander Technique and one thing I have found is that what my body tells me is okay use, is often not good use.
Even mindfulness exercises could help.
Just a few suggestions.