If you have CFS/ME then you will have large amounts of histamine in your body.
To help you sleep and to restore your body clock, B12 works extremely well. Take 1x5mg of Methylcobalamin with breakfast and see how you go. Then increase the dosage and take 1x5mg before bed. Doubling it could help because B12 in high dosages increases TH1 suppressor cell activity which lowers the production of IgE antibodies which will be a problem with Increased Intestinal permeability Syndrome (Leaky Gut).