i have a 15 mo old sw cah he is 21 lbs and he is on 4.5 mls of cortef  broken up into 3 doses.  he is also on .2mg fludrocortisone once a day.  he just had his levels checked and the doc said his levels were good he was not oversuppressed at all.  mybe the dosages need to be lowered for your childs age.  i know all children are different but maybe you could suggest it to your doc and if you still fill uncomfortable about the decision get a second opinion.