HEPLPLEASE

is it possible not to have a "period when you're on pills(21)? im on my 4th day of 7day free pills and still no signs of bleeding. we actually had sex on the last 3 active pills. is this because of the possibility of me being pregnant??? i will start my 3rd pack of BC after 3 days. what do you think ladies? i have my bleed last month on the 5th day of my 7 day free pill.