I had sex a week before my period was supposed to come and today is day 4 of my period not showing up . could i be pregnant ?

Its possible,: Pregnancy is one of the more common causes of missing your period. If you want to know you could do a home pregnancy test. They are available at the pharmacy with no prescription. There are other causes of missed periods Best wishes!

Test for pregnancy: Between day 8-21 of your cycle, counting from the first day, is considered fertile or usafe. Since your intercourse was close and calculations can be off by a few days, you shoukd test yourself fir pregnancy to be sure.