chance of pregnancy?

Erin
Hi guys, my last period was the 25th of July and ended on the 1st, which is the same day i went on the pill and had sex that night and well, pretty much every other night until the 5th. But i was reading online and found out that unless you take your pill on the first day of your period you wont be fully protected and will need to use back up protection? So I'm just worried about the possibility of becoming pregnant? Thank you so much any reply is helpful!