weird spotting?

I've never had any spotting before. My periods are relatively normal. I've already had my period this month- after the last time I had unprotected sex (he pulled out and I'm on the Pill). But today when I went to the bathroom and wiped there was blood. You can spot when you're pregnant right? I don't want to be another one of those girls asking if they are pregnant, but What are your first thoughts ?