How Many Days After I Stop Taking Regestrone Will I Start My Menstrual Cycle?

Hello! I'm 28 years old & going to get married in Feb. Last year i was diagnosed with PCOD but i was having my regular periods. This time i missed my periods. My LMP was 13-10-2010. I consulted a gynaecologist & she has prescribed Tab. Regestrone for 5 days & has also started Tab. Metformin 500mg. How many days after i stop taking regestrone will i get my periods & what if i don't? Will i be able to conceive?