Hi I'm 17 and I take birth control everyday. I had sex with my boyfriend while on birth control and we use the with-drawl method as well. As he pulled out I realized that I was taking an antibiotic and my risk for pregnancy increased because of possible pre-edjuculation even though my boyfriend and I have not encountered it yet and I was on my fertility period. I called my pharmacist and she said that it was very rare for that antibiotic to affect birth control. Just to be safe I took next choice 4 hours after sex. I took my regular birth control pill the next morning and the second tablet 12 hours after the first one. I have had all my regular period symptoms, backache, cramps, acne but no spotting or period which is suppose to be today. I was wondering if next choice is delaying my period or if I'm pregnant. PLEASE HELP! I'm so lost and I can't stop thinking about it.