can you get pregnant if....

erin
okay so this is my third pack of birth control. later today i will be taking the wednesday pill. last month around the beginning/middle of the month i was on antibiotics. i had sex with my boyfriend twice yesterday using the withdrawal method without him peeing in between. i should be fine on no pregnancy scares, right? i am on the pill. sorry if this is a stupid question, i get so paranoid !!