Progesterone 200mg twice a day, is the dosage too high?

Hi, I am 39 years old.  My first pregnancy ended with miscarriage at 45 days.  This time the doctor gave me Progesterone (Prometrium) capsule, 200mg and twice a day.  On day 28, my hcg is 2100 and progesterone is 7.81 (this was before taking Progesterone), then on day 33, my hcg is 18,000 and progesterone 17.54 (after taking it for about 5 days).  I am still taking Prometrium 200mg twice a day (virginal).  As I saw some of you taking Progesterone 100mg, just wondering if the doctors reduced the dosage after your progesterone level increased?  What is the dosage do you usually take?  Once or twice?  Please share your experience.