Progesterone dropping?

B
My doctor just called and said they will set up my early ultrasound for next Wednesday I'll be 5w2d. My doctor feels confident we will be able to see something due to my high HCG levels. They also told me my progesterone dropped to 9.6. Has this happened to anyone? The doctor isn't concerned by it, but I kind of am. Anyone have any insight?
3w3d - HCG 86 Progesterone 16.2
4w3d - HCG 1159 Progedterone 9.6