If you take the progesterone before ovulation, it will stop ovulation, it just won't happen. Like leighanne143 said, you wait 3 days after the LH surge, you have to use some type of ovulation monitor or the little pea strips so you know when it happens. this last time that I got pregnant and was tired of doing all of that, I didn't really know when I ovulated, I had an idea, but not the exact day of the peak of it, you know?