Can i be pregnant after taking plan b and having a period??

Patient: On September 3rd and 4th 2011 i was on vacation and had unprotected sex with my ex boyfriend. On September 6 i took the Plan B pills. September 17 i got my period. After taking Plan B pill i became sexually active with my husband. I am now pregnant today (January 24th 2012) i am 15 weeks and 3 days by ultrasound. Can i be pregnant from my ex boyfriend???