Hey, she's right about the fluctuations during the day. I am taking a natural progesterone supplement. Its called Pro-gest by a company called Emerita. The natural form has no risk of side effects to the fetus and is absorbed very efficiently through the skin. Also you don't need a prescription for it. You can pick it up from most health food stores or buy it online. Good luck to you! It sounds like your levels are great!
Progesterone above 20 is great! Your levels will fluctuate throughout the day so it is possible that the "drop" was just that your progesterone was low at that particular time of the blood draw.
There's no harm in taking the supplements (I'd do oral supplements, aka Prometrium, as opposed to suppositories since your prog. is above 20) if it helps to ease your mind. You'll have to stop taking them by week 10-12.
I was on Prometrium this pregnancy and I'm now almost 34 weeks! I think I was about 10-11 weeks when I stopped taking it.