Taking charcoal 2 hrs away from medication hinging on normal physiology is more or less benign. Are you really fat? The body likes to store stuff in fat like components of plastics.
Take electrolytes not just salt, try a handful of essentially amino acid pills not branched. Try coffee or tea. None of these things if they don’t have crap added to it will break your fast. My guess is you’re low on magnesium.
I would not be overly concerned about headaches, minor discomfort, and other aches and pains. They almost always diminish and eventually go away. Yes, in normal life, aches and pains are your body telling you to do something because something is wrong. But during a prolonged fast, E.G. a 21 day, you will go through minor side effects which are a normal part of the detox and repair processes. If you immediately jump into the medicine cabinet or kitchen in search of SOMETHING to take away my XY or Z every time you feel anything slightly different it will not benefit your fast. Trust your fasting body, it’s a great machine, it rarely needs to be tinkered with during a fast. Let it do its thing, relax, go with it, rest, and only drink water if you are thirsty, and avoid drinking or taking anything else that might impede the work that’s in progress. You’ll be fine and you will reap the many life-changing benefits of a successful long fast.