Low Progesterone

Has anyone had low progesterone early in pregnancy? I am 5wks 3 days and have had a couple days of light brown discharge. My OB said it was likely that it was old blood from implantation but suggested I come in for labs to check levels. My hcg came back 2126 which was OK but progesterone was low at 6.95. I will have more labs in a few days to see if it doubles but just wondering if anyone else had a similar situation and what the outcome was?