As far as I know the symptoms you are discribing ARE a sign that you are detoxing bromide etc.
You need to add salt loads to push out the bromide. It will prevent headaches, brainfog and fatigue.
I only take 4 drops Lugols as of yesterday. Even at 3 drops, if I didnt do a salt load I would get all of the above - major brainfog, headache and I would feel very tired.
I now do 2 salt loads, one first thing in the morning and one early afternoon. I feel great all day. I use right inbetween 1/4 to 1/2 tsp dissolved in 4 oz warm water followed by 12 oz pure warm water. I found this works best for me right now.