i started an antibotic cerfuroxime last week because of some symptoms i had that werent going away from my doctor. ive been on the pill for a month, (migrocestin), and i had no idea that taking an anticbiotic could screw with the birth control pills effectiveness.. ive had my period the last four days, and since it was light the other day, my boyfriend and i had unprotected sex. really worried. if i was on my period, and had unprotected sex, AND am on an antibiotic am i going to get pregnant?