you only take isocort if you are low on cortisol. are you? i have AF but am high in cortisol, so adding more would be a mistake. first you need to know that. as for feeling well, then crashing? yes, i do it to. you are most likely eating something that disagrees with you. you need to do a blood test to see if you have food allergies . diet is key. for me it can be the smallest thing, even chewing a piece of Sugar free gum, Aspartame bothers me.