Could I be pregnant?

I am on the pill but during my period I was taking antibiotics. I had unprotected sex the day my period ended while still on the antibiotics ( the 11th). This past week and a half I've been feeling nauseous at night and very tired all day. This morning I woke up and all day have been feeling like throwing up, certain smells or even thinking about them make me sick. My period is supposed to be on February 3rd but now I'm scared I might be  pregnant. Could I?