Will Periods Start In 5 Days After Taking Progesterone Tablets?

hiii doctor, i had missed my periods, now it is 45 days after my last period. 1 week before i had a blood test and had done the pregnancy test and seen the result as negative, yesterday again i went toa gynecologist and he had prescribed progesteron tablet for 5 days, 2 times a day and said that after 5 days i can expect, can u clarify me on this, i already have a baby boy who is 1.5 years, and i amnot planning to be pregnant again now, what i have to do, please reply.4