I'm going through the same thing. I didn't ovulate last month after being on prometrium (100mg orally). Today my nurse midwife told me that prometrium does stop ovulation in some people, there is no way to know how each of us will react. So, being that my period started yesterday she told me to stop taking it until I start ovulating, and then start taking it again.
This is all so stressfull. She told me that we just have to play with the medication until we find what works for my body. My guess is that is the same thing that your docs will have to do with you.
I'd love to keep in touch with you and find out what your docs say and what finally works for you.
Hope to hear from you!

Devon

I have been given Prometrium to start my period, because I had gone 70 days with out a period and not pregnant! I was told to take Prometrium once a day for five days and then wait for my period to start a couple of days later because we are trying to conceive. My last dose was Friday and AF came today. I was told to then test for OV around day 10-14. I am supposed to continue taking Prometrium at the same time each month and checking for OV. If no OV after 3 consecutive months I will have to try something else.