Someone please ease my mind ..

I take my birth control pills RELIGIOUSLY. I've never ever missed a pill. Take it the same time every day. And have been on the pill for two years and have always gotten a period every single month. Monday. Before 12 pm the latest. I have unprotected sex with my boyfriend and I'm supposed to get my period today and still have not gotten it. It's now 3:36 PM and I have no cramping whatsoever. Usually I wake up with cramps and will get it a few hours later. Today nothing. Is there a chance I could be pregnant ..