If your progesterone is low you are at extreme risk for miscarrying. I know alot of girls that have to be on progesterone pills or shots just so that they can stay pregnant. If your luteal phase is within the normal range of 10 to 16 days then I don't think you have anything to worry about. A 10 day LP is the minimum though and it is better to be around the 12 day mark. It is not impossible to stay pregnant with lower levels of progesterone but it does make it pretty tough.
Progesterone is check at 7dpo through a blood test. What is your LP length?
Bumping for more help for Once Blessed too!