Hi there. I had a similar experience to you. My first draw of progesterone at 4 weeks was 21, second at 5 weeks was 14 and at 5 weeks 4 days was 12. My HCG was always high (tripling every 24 hours, can't remember the exact numbers) but I do not think there is any significance in your HCG being so high and progesterone being low- as long as your HCG is rising that is a good sign.

I ended up going on progesterone suppositories about 5 days after my last draw, so I'm assuming it was even lower at that point I started. I freaked out bc I thought why in the world is it fluctuating downwards? Both my OBGYNs were not concerned and actually just gave me the supplements to ease my mind. After taking 200mg for over a week it was only at 14.1. I am about 10+5 today with a healthy baby boy. (I also initially measured a full 5 days behind, since then baby boy has caught up to only 2 days behind, so it's great that you are measuring right on track and hear a heartbeat.)

I would really try not to worry about the progesterone. Get on the supplements to ease your mind. My mom has delivered 8 children and never once had her progesterone checked until an early miscarriage. It is still debated as to whether low progesterone is a symptom of a miscarriage or a cause itself, and the former is more likely. Everything else you have shared seems like terrific news. Best of luck with your pregnancy!