question: Hello doctor, My friend and I had sex on the 29th of last month. Her last periods started on the 15th of last month. We used a condom the whole time, but I was worried there could have been a leak and got her an I-pill within 18 hours of intercourse. She has had no bleeding whatsoever since then and not even had her periods yet. Is there anything to worry? She normally gets her periods in 28 days. Please help.