When Should Periods Be Expected After Taking Primolut-N?

My mestuation is around 35 days. Last month it was few brown drops for 4-5 days. I went to the physician and he gave me primolut n 5mg twice a day for 5 daysstarted on last 17th of march. Till now there is no bleeding and I am afraid of being pregnant! Is it impossible to get pregnant with this medicine? What about the ovulation and when I get menstruation?