Took antibiotics while on birth control can i be pregnant?

I have been on the pill for 8 months, and about 2 weeks ago i was on antibiotics called-ponstan forte/zyrtec/apo-ciproflox on the day of my last pill through my menstrual cycle and then 3 days into my new pack, according to my calculator my most fertile days were through nov 29-dec 1 ....but me and my husband had on the 29 and they say sperm can last up to 3 to 5 days....what are my chances of being pregnant? should i keep taking the pill where im not sure....???