Suggest Medication For Delay In Periods

Hello. I am sending this e mail because I wish to hear advice from a doctor. I had my normal regular period 5.6.2014. I had sex 13.6 and i took EllaOne pill that day. My normal next period neded to be here 3.7. Today is 10.7 and it is still not here. I feel some small pain in my down part but nothing more. So is it normal that period is not on time like this 7 days? Thank you..Mary