If your morning cortisol is low, that probably means you are at a later stage. However, mine is always high, even when I had all the symptoms of Stage 3 and even some Stage 4 symptoms (Dr Lam stages)
Here is a excerpt from one of Dr Lams pages.
Furthermore, in advance Adrenal Fatigue, the 24 hour saliva cortisol curve invariably becomes flattened most of the time and can stay that way for an extended period of time, even during recovery.