Hello, I Was Supposed To Get My Periods On 19th

Hello, I was supposed to get my periods on 19th of this month but not yet got it. As I'm going out of station next week I want to to get my periods as soon as possible. So I consulted my doctor. She adviced me to take regesterone for 2 days thrice a day n stop it. So after stopping wen can I expect my periods. I want it as early as possible pls help..