Progesterone levels dropped

I got a BFP on 2/17. Went to the dot on 2/20. Pee test came back positive. Got labs drawn. My progesterone was at 10.7 and hcg was 61 at roughly 3 weeks 5 days according to LMP.

Doctor had labs drawn again yesterday and my progesterone dropped to a 7.4. Doctor called to day and said he wants me on 200mg of progesterone 2 times a day. I haven’t seen the results of the hcg yet so I’m not sure if they have doubled.

AF was due Monday 2/25 and still hasn’t shown up. I had a miscarriage last August so I’m nervous. He wants me to come in tomorrow for an ultrasound.

Has anyone dealt with this and had a good pregnancy?

***UPDATE: went in for an ultrasound today and they found a gestational sack measuring right on time at 4 weeks 6 days. I will stay on progesterone and have another ultrasound next Friday.