It is best to have a colonic 2 to 3 days after the flush. Yes these headaches can be due to toxicity released from the liver and become partially reabsorbed. If you could get the accupuncturist to stimulate the gallbladder/liver meridians it may be quite helpful for your flush. Tell him/her you intentions so they can stimulate accordingly. Should be quite beneficial I would think. As far as fasting goes, you may just want to observe the fasting rules that are part of the flush for now. You may even want to consider utilizing castor oil packs on your liver area leading up to the flush.