This is a bit hard to explain but I will try to while I am still able ... I had the CFS for 18 monthes now and it never switches off, its always there even when I feel reasonably normal and I always get all of the textbook symptoms post exertion, however there has been distinct periods of ' reasonable stability / predictability ' and ' extreme instability / volatility / unpredictability '. For the first 6 monthes of the illness I had 'stability', was able to do quite a few normal activities but with acute PEM consequences at times as a result, was able to do medium construction work for example, building wooden wall panels etc. Then 11 monthes ago something changed, it happened over the course of about a month but the initiating factor seemed to be when I tried to do ' GET ' style exercise, I wasn't sure if I had CFS at that point so I was just following what a doctor told me, this exercise was low to mid intensity aerobic but at a high duration / frequency, so harder than walking but not enough to cause crashes, the idea being to get more proficient at it over time. The first sign of the ' secondary disease process ' was a sort of chemical burn looking allergic reaction on my index finger, it then caused the finger to become ' arthritic ', which spread to my other fingers and toes, then later red marks on the back of the hand started to appear. [shown here ] http://i.imgur.com/nspAq4L.jpg Not long after that started I had a major crash which left me in bed for about a week, after which I struggled to walk even half a mile anymore and I would get crashes and brain fog more frequently even without leaving the house / exercise, so I became quite physically inactive, also started to have more orthostatic intolerance. After about a month of that I had a period where I had near constant crashes / laying in bed, then became severe after a particularly bad one, this lasted about a month and then I recovered somehow back to moderate and the 'secondary disease process' then deactivated somehow. So in total that period of 'instability' lasted for about 4 or 5 monthes, then I had a period of about 5 or 6 monthes of 'stability',. About a month ago though I ran out of the drugs I was using for pacing management ( beta blockers, ssri ), and I lost control of my pacing to an extent, then because I already was staying up until 4 or 5 am I stayed up until 8am to see the doctor, then my sleeping pattern got totally removed and I also picked up a flu virus or something which tends to happen when I go anywhere with lots of people, so I got into a situation where I was constantly really tired but couldn't sleep for more than 4 or 5 hours, so I was sleeping 3 times as much for half as long, which I started to think I would never break out of but did after a couple of weeks, then around that time I had a 'nervous system overdrive' crash because of several days of trying to keep up with teenagers in a game. Then after that I had people doing construction work at my house which to start with forced me to go into my room at the end of the garden which I didn't feel like doing, until I figured out I could reduce the noise reasonably well with military grade IEM earphone tips, but it became increasingly difficult to walk and reach some things in the kitchen which were unnaturally further away since december time, I also was starting to go insane from the constant noise / extra people, because I wasn't getting the chance to 'turn my brain off' like I normally would. So that was the situation 1 week ago, so I remember thinking on the saturday that this is when I should really be resting, although I ended up using quite a bit of energy because I wanted to test a VR software that I pay somebody to make, so its like dancing and pornographic scenes etc, so after that day I felt different and I realized that my body had switched into a different mode, which I could tell was the same as what happened before, then even after 5 or 6 days I still couldn't tolerate any physical activity, I did something that shouldn't be a particular problem yesterday and getting a lot of consequences from it to the point where I'm considering stopping playing video games entirely for a while because my body feels really sensitive to any sort of exertion at the moment, I get the feeling that it could quite easily get back into that 'severe' state if I'm not extremely careful. It seems like there is some sort of 'switch' that turns on when the body is stressed / drained over a period of time, and it seems secondary to the overall CFS disease mechanism rather than scaling off of it. I don't really know how I managed to switch it off last time, it only happened after I became severely ill. I didn't recognize it as being secondary before and therefore I didn't think it would switch back on again.