thanks tania, you made a good 'catch' on my post, I was in a hurry when I wrote that and on re-read it could be misunderstood, your clarification was correct and appreciated!
hensue, ME/CFS takes time to diagnose, even in the best situation. Actually, as hard as this might sound, if your son has ME/CFS he is probably better off than some of the other possible diagnosis, as there IS chance of significant recovery in the early years and we know a lot more now about how to treat ME/CFS now. I do know people who have worked on their health and experienced significant remission within the first five years or so.
Also, I relate to your situation as I both have ME/CFS and have a child, who is also an adult, who also has ME/CFS, plus FM. She had to drop out of college due to getting this illness and has lived with us ever since. This was very hard for me to accept the first few years, she was very bad off at first, did not have the energy to leave the house for about two years at one point, she actually never even went out the front door or even sat on the porch. I remember the day she finally went outside. We have continued to work, every single day, on this illness, for years, and have made significant progress. My daughter went shopping today for about two hours, with her mother, standing up and walking around, etc. She can drive again, reasonable distances. Still sick and disabled, and she still has to monitor her energy envelop carefully and take supplements, including active B vitamins as tania pointed out. But she is more functional and life is better for her.
I hope you and your son find a way to make peace with your situation, there is a LOT you both can do, and there are doctors and also natural medicine experts who probably can help.
One medical thought occurred to me, since you mention your son has liver area pain, the liver holds the largest reserve of glutathione in the body. So logically, if he is having Phase I/II detox problems and glutathione is being depleted, and/or methylation is getting blocked, the liver might be very distressed. Also, the liver is a primary target for the autoimmune condition that might be involved in ME/CFS (anti-cardiolipin/anti-mitochondria), per a study in Hawaii. Of course there may be many different problems with the liver, this particular methylation/detox problem just happens to be one that appears common in ME/CFS. Fortunately that is a system that can be helped with supplements (methylation is involved in the level of glutathoine in the liver). That is just one example of how digging in and learning might lead to some help, while we wait for better answers (collectively speaking).
Regarding whether your son has ME/CFS, PEM is a pretty strong indicator for this illness.