Progesterone prescribed - What to expect?

Hey, mamas. This is my 3rd pregnancy and it will be my first successful birth, I'm praying. I was just prescribed progesterone to take vaginally because my provider said I was on the low end of normal. To ease my mind while waiting for the first appointment, I decided to ask for labs yesterday. At 5 weeks 4 days my HCG was 9,739. I go back for follow-up labs tomorrow to make sure it is rising appropriately. My progesterone level was 16.70. She said she prescribed it out of an abundance of caution. Anybody else ever been in this situation? My symptoms have been mild (exhaustion, off and on sore breasts and mild cramping). This just added to my anxiety when I've been feeling so much more optimistic this time. I know it varies per person, but any side effects I can expect? What were other's progesterone level at this stage?