It seems that Dr. Goldmeier indicated to you that you may have CFS as a result of POIS. This would probably mena that it takes longer for you to recover, because the constant POIS "beating" deplete your system beyond the normal. I think it may be true for many of us too.
POIS is a heavy load on the system, depletes histamines and many base raw materials that would otherwise contribute to mental stability. So although POIS has a cycle time of 6 to 14 days, CFS side effects may not let us recuperate well in between.
To cure CFS we need to cure or abate POIS. So your desensitivation is a good move, so would be niacin, which reduces the depletion.
Keep at it.