I have been on birth control for years but was taking a 10 day antibiotic and my boyfriend and I had unprotected sex. Although he didn't cum inside me, he went back if after he "finished". I am just a little worried since I know antibiotics can effect the pill and I was on day 9 of the pill which means day 12 of my cycle (high fertility chance). I took plan b within the three days after having sex as I was super paranoid. I want to know if I should still be worried? Thanks in advance for your response!!