Can I be pregnant after a "period"?

In early September I had unprotected sex (came inside me) and I took plan b although there were other times that were unprotected (he pulled out). My period came early and its lasted 3 weeks, mostly very light. I've gotten worried the past few days because my boobs have suddenly gotten bigger and sore, and out of nowhere I threw up the other day. Is it possible for me to be pregnant even with this bleeding?