Had unprotected sex on 7/26 around 12 a.m until 3 a.m. period started on 7/29..period lasted for 5 days, normally lasts for 6 or 7days.could i b preg?

Unlikely : If you have regular periods (every 28 days?), it's highly unlikely that you are pregnant. If you are not interested in becoming pregnant, you should consider a reliable form of birth control (pills, IUDs, nexplanon (I don't recommend Deposit Provera). Also, remember that Plan B (over the counter medication) is a last resort option. Also, you should be on prenatal vitamins.