Could I be pregnant?

I've been on the birth control pill Junel Fe for about 4 months, and I have never messed up on taking it. Once I started taking it my average cycle went from around 27 days to 16 days. Meaning I would get my period about every two weeks. I had unprotected sex when I was fertile 2 weeks ago, the birth control methods we were using was the pill and withdrawal. My period is 13 days late now and I'm scared that I may be pregnant.. What should I do.