My first blood draw, my P4 level was 12.4 ... A week later it was down to 11.5. My doctor was not all that concerned, as some just like to see it over 10 in the first few weeks, and my betas were rising appropriately. I really pressed her for progesterone supplements after seeing the heartbeat at 6w4d, and she agreed that she'd feel more comfortable if they were over 15. I am on 200 mg of Prometrium twice a day, and I just take it orally. If you are doing a progesterone suppository, like Crinone, most come with applicators.
Good luck! I hope it makes a difference for you.