Progesterone levels?

I am 4w5d. I had my progesterone tested last Wednesday and it was 23.7. I had it tested again yesterday and it had dropped to 19.6 :/ Is the pregnancy in danger? Is or has anyone experienced this? Hcg was 250 last Wednesday and 4500 yesterday. It's my first pregnancy, and I am just a little freaked out. Thank you!