i agre with pp, im the same i have a son who has adhd who is 3 n im due to pop so my days consist of up n down stairs n in and outside etc u could imagine..
i was going to suggest ur iron n stuff but if they are all fine i would be stumped too.. maybe as a pp said the food ur eating?? if its tired as in cause ur running around all day after him then i would say we r all in the same boat but if its more than that i would consult ur dr again till u have a solution.. GL