OPK help! Negative with FMU, positive this afternoon

Ashley
I've been tracking my ovulation with a clear blue advanced OPK this cycle due to lack of AF (and ovulation) the last couple months. I was put on 10 days of provera, which induced a period within 2 days of the last pill. The doc wants to see if I ovulate on my own. I tested with FMU today and got a negative. Then started to have some cramping during the morning, so after I got home from brunch I took another test and got high fertility (blinking smiley). Is that normal? Thanks to all who can help!