Please note that the menstrual cycle has safe period and unsafe ( fertile period).If sex  happened during safe period there is no need of i- pill., provided her periods are regular. Safe period & unsafe periods depend on how often a woman gets her period .For example if period occurs every 28 days,then safe period would be from days 1 to day 10 and  day 22 to day 28 and I.,e  no  need of  i- pill if sex had  during  the above days. Hence kindly check when your days of having sex  fall. ,