I was in the exact situation as you but my doctor did nothing and I lost my baby girl 3 weeks later. I have an appt. today for a second opinion about why my dr. did nothing because I was told also on this forum that prometrium works and so I'm thinking about sueing him. I'm sure you'll be fine now and I wish you the best of luck.
Mine was 20 but dropping. It went from 20 to 16 to 11. I was put on progesterone suppositories (crinone brand) and my son was born 3 weeks ago.
Best of luck to you and congrats.