I Am Currently On Zoloft And Lo Loestrin Fe Which

I am currently on Zoloft and lo loestrin fe which I usually take together. I have been taking the li loestrin fe for 4 months and have had a regular menstrual cycle until this month. During this month I have also been on antibiotics and my husband and I have had unprotected intercourse multiple times. I am now twelve days late and have recently taken two pregnancy tests (mid day) which were negative, should I be concerned?