Does Stopping Regestrone Commence The Periods Immediately?

hi .. i was getting brownish discharge till 13th day of period when i saw a doc , and she suggested me to have regestron for 10 days , post which she said i'll get periods the next day and then few more tests were prscribed .. now its has been 3 days, i 've stopped the med and i have not got my periods.. anything that i shd worry for , or it takes few days for periods to come after stopping medicine