What to do if i had sex 3 days ago while on the pill and now i need to take antibiotics?

Overhyped...: Contrary to popular belief, most common antibiotics don't seriously affect birth control pills. Rifampin, used to treat Tuberculosis is an exception. Penicillin, amoxicillin, ampicillin, sulfamethoxazole/trimethoprim (Bactrim), tetracycline, metronidazole have a small effect but pregnancy from this is very rare. Take the antibiotic and use a condom if you have intercourse. Best wishes!