is basically caused when your body becomes stuck in the "stress mode," known as the Fight or Flight response -- or technically called Sympathetic Dominance or Amygdala Hijack. Usually you're in this mode for constant stress and/or unresolved emotional baggage and then you get a virus outbreak, like Epstein Bar/Mono, that that sends your body over the edge and into CFS.
In theory, anti-anxiety meds (whether natural of pharma) can help calm down your stress response, but it will probably only bandaid it.
To get out of Sympathetic Dominance, try some energy psychology techniques like EFT, Healing Codes, Emotion Code, Lifeline technique, TAT, TFT, etc. that deal with the underlying emotional root causes.