Birth Control and Antibiotics with Unprotected sex?

Patient: I have been taking Tri-Sprintec for over a year now. Last Tuesday I went to the doctor with a sinus infection and I was prescribed Ciprofloaxin. I began the antibiotic that night and (forgetting that I was on antibiotics) had unprotected sex Wednesday. Wednesday night I didn’t take the antibiotic and haven’t since. I did, however, continue taking birth control. I have a phobia of getting pregnant anyways, but now I am very worried. Two days ago I started my week of placebo pills. How worried should I be about being pregnant and what should I do now?