My period ended on a Saturday,I started taking my contraceptives the same day,I had sex 4 days later,is it possible for me to get pregnant

Any time you have sex, protected or not, it is possible to become pregnant. The chances are much smaller while on birth control pills, however, so it really just depends on your pill. What did the instructions say. Many pills will state that they become effective within 7 days of starting them, but I have also been told by doctors that if they are started with the end of a period, they are effective immediately. Keep in mind, though, that millions of women become pregnant while on birth control pills, myself included. Good luck!