My Periods Are Irregular Usually Last Time I Got Periods

My periods are irregular usually last time I got periods on 26/12/2015 I have an intercourse on 9/1/2016 he used condoms then and after intercourse I had taken new pill tablet with in one hour from the day of intercourse I have taken vitamin c tablets for three days till today iam eating sesame seeds daily yesterday I have eaten papaya today is 27/1/2016 still I didn't got periods I don't want to be pregnant what I have to do to get periods?