Progesterone dropped while on supplements

So I found out I’m pregnant over a week ago, at 3 weeks 5 days. My doctor had my progesterone tested the next day because I miscarried in February most likely from low progesterone. It was at 16.5 when I was tested on 6/13. She had me start 200mg orally at night immediately. I was tested again this week on 6/20, and my levels had dropped to 13.5. Has anyone else had this happen? I’m now taking 200mg twice a day vaginally and getting tested again next week.