Antibiotics and birth control

Patient: a 17 year old female and this is my second month on birth on the pills 21 days long and than i have a 7 day break and during those 7 days i always get my period(usually on the 4th day) but during my 7 day break i was on antiobiotics and had sex before and after my period.on the 8th day i had the last antibiotic and my first birth control pill(the 2nd box).should i be worried about being pregnant? thank you