progesterone level- help!

SA • Wife & Mother. Son & Daughter, toddlers. One year apart.
I just got a call from my OB office instructing me to pickup my progesterone prescription from the pharmacy and start using the suppositories tonight. I wasn't even aware it was low. She said my level was at 7.3. Do levels this low ever result in healthy pregnancies? I didn't have this issue with my first at all. I'm so upset and can't stop crying. Any experiences?