What Causes Delayed Period, Dizziness And Lightheadedness While On Birth Control?

I ve been feeling super dizzy and light headed all day. I also have been feeling a bit nauseated. I accidentally missed a day here and there this month on my birth control but I took that pill I missed the next day. I had unprotected sex 2 days ago and he did not pull out. I was supposed to start my period today and it is not here. Could I be pregnant or am I just freaking myself out?