Low progesterone could be part of low cortisol, which would explain lethargy at a particular time of day.
I would like to see a cortisol test done at the time of day when lethargy is greatest. Travel to the lab and blood draw might create a cortisol increase reflex which would mask the problem. If you find that lethargy is reduced when getting labs done, cortisol lab results may not reflect your normal levels at that time of day.
More cortisol: How do you react to major stress? If cortisol is low, rT3 may be elevated.
Thyroid: Do you get cold easily? What is your iodine intake? [vitamins, iodized salt]
DHEA levels change a lot, DHEA-S is a better DHEA status indicator.