Progesterone drop at 5+5

Hi everyone. I’m supposed to be 5 weeks 5 days today and here are my results so far:

5/15 - progesterone: 27 - HCG: 160

5/17 - progesterone: 38 - HCG: 394

5/20- progesterone: 19.8 - HCG: 1,020

I have been on 400mg of oral progesterone since my bfp however as you can see, my progesterone dropped from a 38 to 19.8 in 3 days. My OB advised to increase dosage, so from yesterday When I got my results I started taking 800mg orally. She said the increase in hcg is reassuring but I can’t help but worry since last year I had a missed mc. I got bloodwork done again today and should get results tomorrow. I did read about progesterone fluctuating and on the day it dropped I had my blood drawn after eating whereas the other 2 days while fasting, praying that had something to do with it. Please share if you’ve went through anything similar.