Jackie are you drinking at the very least a gallon of water a day plus 16oz. of water after every dose of IF#2 and the charcoal? If you're not drinking enough water that could account for the constipation.
The problem with the headaches; are you still taking prescription drugs for the them? I ask because with taking the charcoal it will adsorb drugs that are in your system, not all of them but the charcoal will adsorb a percentage of them. If you're still taking something for the headaches maybe you're feeling the headache more due to a percentage of the drugs being adsorbed. Just a thought.
Blessings,
Willow