What Causes Prolonged Periods After Taking Plan B?

I took a Plan B about a month ago after unprotected sex. Engaged in the same activity a few days later. Since, I have noticed that my body seems to be chemically off. Had a period for 2 weeks, approx. 2 weeks ago... Starting on my regular cycle now, but the blood is orange. Think it's time to see the gyno... Any ideas what I am up against?