I'm actually not sure why my doc had me do the progesterone. I had mine tested last cycle, and it was 13, which I hear is in the normal range, yet, I've had some issues with spotting, so my doc thought he'd give it a try. My luteal phase ranges from 11-12 days, and today I'm 12 DPO, and still no AF. I was actually up half the night due to terrible nauseau, which then turned into diarrhea. (Sorry for the gross detail!