I was on antibiotics due to a sinus infection a week ago.the 5 day miracle pill..i started that March 4th..The doc said it stays in your system for 10 days. I also started my period March 4th.. And ended it March 9th. I started my new pack of birth control March 10th knowing the antibiotics could knock it out still..March 12th I had sexual intercourse unprotected.I havent had any signs of pregnancy..(which i wouldnt expect so early on in the game.) But my vaginal discharge is dry.