I'm sorry but I do not know what magnescent Iodine does include, Iodine and potassiumiodine? you will need both. also, if you feel side effects these will be most likely because of the bromide Iodine releases from the cells which is good because its detoxifying your body but bad also because until its out of the body bromide is active and causes these side effects. so you should salt load.
and you need to take selenium with iodine because otherwise the thyroid does not have the necessary build blocks to build t4.
also, if you do all of this stuff and try to speed up your metabolism by doing cardio you will definately see results and have less side effects.
beeing tired could be the combined effect of the free bromine in your body and your body beeing in "eco mode" if you are not doing any activities?