What Causes Light Bleeding With Back Pain Before The Periods?

Hello, I had unprotected sex using the pull out method on my ovulation day. It is now about two weeks later, and about a week before my period is due. I am experiencing light bleeding when I urinate. Mostly when I wipe. There is no clotting. I have never had an irregular cycle. It comes like clockwork. I am experiencing mild cramping and siatica pain. My period is normally extremely heavy from start to finish lasting five days with bad cramps so this is not normal. Could I be pregnant?