progesterone pills?

I met with my doctor today to talk about my blood test results. My hcg was only 23, and I was maybe 9 DPO when they drew blood and about 2-3 days after implantation. She didn't seem worried about the low number because it's so soon, but she put me on progesterone pills (400 mg a day) because my previous miscarriage was most likely due to low progesterone causing my HCG not to rise. Anyone out there have success with progesterone helping them keep a baby?? really hoping for some stories to make me feel more hopeful.