Birth control pill help

I just started chateal EX 2-10 i was in middle of cycle when i started taking the pills my period was due 2/16 and i still havent received my period yet. Im confused on why, could it be because im still on the active pills? And it caused me to skip it? Or is there a possible pregnancy chance?? What confuses me is it takes a week to become effective (what dr said) so i thought on 2/17 it would become effective i dont see why i would skip a period?