quick question-- i'm a 28 year old female who's been on zenchent (birth control) for years now and take it regularly everyday-- i've recently had a cold and have been on amoxycillin.. i didn't take any friday, saturday or sunday and just one pill monday.. i've heard that the antibiotic can sometimes interfere with birth control, is there any reason i should be worried if i had unprotected sex tuesday or is this a small chance that it could interfere?