I am not sure what andestron is and what is treats.
As for the cortisol, you did not say the dose. One normally take the bulk of the dose for day, of say, 20mg, on waking and then the 5 mg at 3pm. This way you mimic a normal a normal body. Taking it all the time is not optimal unles you have too like if you are sick.
Nausea is typically a sign you are not getting enough cortisol or not dosing right. Look up adrenal crisis. You are may be getting sick. You may need to up you steroid dose to cover the illness. Also up sodium. I hope your doctor covered the importance of sodium.