Low progesterone week 8

I had my blood drawn at week 7 and my progesterone was 8.6. Had ultrasound at 8 weeks and they said the heart rate was 139 and everything looked good. The dr called me yesterday (day after the ultra sound) about the blood work from the week prior. He said the progesterone was “a little low” and gave me a prescription for pills.

I am freaking out because I feel like he should have called me LAST WEEK about the blood test. I saw the baby on the monitor and I thought everything was great and now my heart is broken. Would the baby progress for a whole week if the progesterone was that low??