Okay... so my period has been on a perfect 28 day cycle since I've been tracking it, which has been close to a year. I got sick with a sinus infection and started taking antibiotics..(February 3rd). My period was suppose to come 5 days later (February 8th) but didnt! It's the 11th and I still haven't gotten my period. My question is this: could the antibiotics delay my period or could I be in the early stages of pregnancy?