Thank you for posting your question here, I will try to answer it to the best of my abilities.Stress
can cause the dates of your period change, they can come later or earlier than what is normal for you. An i-pill within two hours of the intercourse was a good move and it should reduce the chances of you getting pregnant significantly.
Take a home pregnancy
test and you'll have the answer you're looking for. Although it highly probable that your period is just late this month.
I hope this answered your question.