Thoughts?

So my bf and I had sex when I was ovulating. We didn't use a condom, but he pulled out to cum. I got nervous and ended up taking a plan B pill just to be safe. Got my period 2 days late, but my "period" isn't like its normal bleeding pattern. I bled very very heavy with a lot of cramping the first day and today it was very light with a lot of cramping. Is the change from the plan b pill or could I be pregnant?