Pregnancy

So I have a question..is it possible to be 2wks pregnant if only had sex on the 2,11,15 of December my bf cheated and now the chick is saying she is two weeks pregnant.and it's.his I.can forgive the cheating but not sure if I can stand him fathering a baby with someone.else we have two boys and have been trying for a girl but now I'm not sure.what to do