Anyone ever take provera?

Lady

I usually have very regular periods. This month, I was already 8 days late with all bfns when we went to see a fertility doctor for a consult. I need my period to start in order for the testing to be done. And I am now 10 days late. The doctor called in a provera script for me and I started it today. Has anyone taken provera before? How many days after did you start your period? TIA