Progesterone importance

I have some concerns about my progesterone levels. I know some Drs say progesterone is everything and some say it doesn't make a difference on levels during pregnancy. I had my first appointment this week (I'll be 9 weeks tomorrow). The baby is growing on track, everything was where it's supposed to be, and the heartbeat was 174. I of course had my prenatal blood work and I asked to check my progesterone. My progesterone levels are at 8.9 which I believe, based on lots of articles and research, is low for 9 weeks pregnant. My doctor was not concerned about the levels and said she would prescribe progesterone to give me peace of mind which is awesome. Is this detrimental or is this normal for where I am in my pregnancy? Any advice, similar experiences, or info would be appreciated.