SK, You didn't mention how often you have the problems mentioned before. There are side effects from taking too little cortef also. Taking a replacement dose of cortef should not cause a problem. I would guess after this long you do not have any adrenal function left. A minimum dose would be more like 15mg.
I am discussing this with you because being ill often is really not part of addisons unless there are other complications or illness like infection or whatever. I have not been sick since being diagnosed & consider myself VERY lucky. I'm sure I will have my turn at it! I get by on 20mg HC & 1/2 tab of Florinef. What I miss most is stamina & strength.
Some people have to increase their steriod dose after an increase in thyroid med.
I am wishing you well & just don't want to see you ill when you shouldn't be!