To me, the two conditions you mention are different. I have chronic fatigue and feel tired all the time, don't sleep well, get all sorts of aches and pains, brain fog, lots of headaches and other stuff but don't have a white tongue. I've had it for about 30 years and hate it. There is no cure and it is certainly not all in your mind. I used to play sport, dance a lot, run marathons all whilst bringing up 4 children. With CFS I am a completely different person, in my mind i want to do everything I used to and more but in fact I just can't, too tired and worn out. It's all I can manage to cook a meal and do a little housework every day. I must just add that there are a lot of people with CFS who are a lot worse than me, some are bedridden and have to be tube fed.
You posted this awhile ago. But Chronic Fatigue Syndrome is chronic fatigue that lasts 6 months or more with no underlying cause that can be found. Here are the symptoms:
Fatigue
Problems with memory or concentration
Sore throat
Headaches
Enlarged lymph nodes in your neck or armpits
Unexplained muscle or joint pain
Dizziness that worsens with moving from lying down or sitting to standing
Unrefreshing sleep
Extreme exhaustion after physical or mental exercise
https://www.mayoclinic.org/diseases-conditions/chronic-fatigue-syndrome/symptoms-causes/syc-20360490