I have CFS and I'm 17 years old. I've had it since I was about 14, and was diagnosed when I was 15. When I was being diagnosed I had a blood test pretty much every fortnight for 6 months as I was passed around doctors and they all wanted to redo every test
My symptoms currently are fatigue, muscle pain (mainly in my legs), brain fog and headaches, but at my lowest points I've had dizziness, nausea, migraines, IBS like symptoms, poor sleep and sensitivity to light and noise, as well as fatigue so bad I couldn't get out of bed and muscle pain that isn't eased by any painkillers.
To cope, I usually take lots of pain killers
I try to get as much sleep as I can, and I sleep when I'm tired during the day, as I find that after a nap I am able to concentrate a bit better and can get some things done. I deal with the brain fog by writing everything down, and explaining to people I can be a bit forgetful, especially when tired, so now my friends know I'm not ignoring them if I forget what they say, and I don't mean to stop mid sentence because my mind's gone blank. The main thing I'd say is don't try to fight the tiredness. The more you try to do when you feel unwell, the worse it'll be the next day. You just have to accept that you aren't well and rest when you need it.
I don't know anyone my age that has CFS/fibro, but one of the teachers at my school has it, and I've found it useful to talk to him, as his isn't as bad as mine and he copes quite well, so he can give me tips for when I'm struggling. He also gave me the name of a specialist in the county next to mine, so I could go to my GP and ask to be referred to this doctor, as the NHS trust I'm in doesn't have any provision for people with CFS.
The main ways it's affected my life is that it's meant my social life has been greatly reduced. I often amn't able to go out with friends as I get too tired, and they don't understand my CFS much so I've lost some friends as they think I'm just being lazy or making it up. I recently split from my boyfriend, who I had been with since before I was diagnosed, and when I asked him about it he said one reason we were breaking up was that he couldn't cope with my illness anymore, which was hard to hear. I hope that one day I'll find someone who'll be able to understand my illness and won't be affected by it, but I don't hold out much hope for that happening anytime soon. Another way it's affected me is at school. I used to be a straight A/A* student, but recently I can't keep up with the workload because of my health. I don't find the work hard, but I no longer have the energy to work as hard as I used to. This has meant I have had to drop a subject in school, and my grades have gone to B's and C's. My teachers understand, but I do feel disappointed in myself when I know I could do better. But I can't do anything about the fact that when I get home I'm in too much pain to concentrate, or I fall asleep instantly and will sleep for 14 or 16 hours straight. I just have to accept that this is how I have to live now and hopefully it'll get better with time.
Also, I was told by the specialist I see that CFS and Fibromyalgia are pretty much the same illness, but most doctors diagnose CFS when fatigue is the main symptom, and fibro when pain is the main symptom. But that's just what I've been told, it might be different in different areas.
Sorry this is a bit long, but I hope it was useful to read. PM me if you want to chat