I was wondering if anyone's progesterone level fluctuated during early pregnancy?

My progesterone last tuesday (4 wks, 3 days) was 22.6 and today (5 wks, 3 days) was 14. I'm a little freaked out by it. The RE nurse said that it is still ok - and they would get worried if it dropped to 11-12. My beta is doubling nicely though. Last week it was 972 and today 9,963.