My period started November 11, 2011 and ended early morning November 18

Patient: My period started November 11, 2011 and ended early morning November 18. My period last month started October 10, so my schedule is usually regular. I just had sex last night – early morning around 2 am, November 18, but the condom slipped off during intercourse in my vagina. He ejaculated in the condom before it came off. When I pulled it out I could see that cum was still inside the condom but not completely sure if anything came out. Is there a possibility that i could be pregnant? Should I take the Plan B pill? Can you get pregnant right after you end your period?

Doctor: