You just have to look at the circadian rhythm of a normal person’s cortisol levels and you will see that the treatment of CAH is far from perfect!  It is impossible to mimic the body and therefore doctors tend to give a little more than they should.  This must compromise the immune system - they also say on replacement doses you should not get osteoporosis and weight gain............ sorry I don’t buy that!  Again some people will do better than others - perhaps a multi vitamins could help?  Good luck and I hope things improve soon