I first had mono for a while without knowing it, and struggeling at swimming practice without being sure why. Then a couple of months later me and my family had a stomach virus or something like that. I had never been so ill in my life, I just remember sleeping for a week, only waking up to drink, and food tasting like blood. When my family recovered, I still felt really ill, so we went to get my bloodwork done after a while and all the doctor found was that it seemed I recently had mono but that it wasn't an active infection anymore. He said I probably only felt ill because of some after effects of mono and that it would pass pretty soon. So I don't know if it was mono that caused my ME, or the second infection or a combination of the two. But I haven't had a day I've felt healthy after I got mono, so I count that as the start of my illness.
The first 3 or so years I would describe as feeling like an active virus infection. I needed to sleep 18 hours a day, and it was almost impossible to wake me up. I had constantly swollen glands, and felt very warm like I had a fever constantly. My PEM/crashing resulted in sleeping a lot. In the beginning daylight was extremely painful for my eyes, while now it's usually not painful, it just drains my energy very quickly and gives me sensory overload.
After the first years it changed. From sleeping a lot, to struggeling to fall asleep. Feeling a lot more of that electric/wired feeling, while the first years was more of a drowsy, sleepy, fever feeling. Now instead of making me sleep a lot, my PEM/crashes makes it very hard to sleep. I rarely have swollen glands though I always have a sore and dry throat. Instead of feeling warm like I have a fever, I tend to feel too cold. The PEM is more severe and lasts longer, and losing function after big crashes is more permanent, while in the beginning I could do pretty extreme exercise, get a crash and sleep a lot, and then get almost back to baseline (baseline was still feeling very sick though).
Some symptoms have always stayed the same, like the constant dizziness and severe brainfog, muscle weakness regardless of my fitness, often shaking from fatigue/exhaustion and getting the feeling of lactic acid build up very quickly.