Late Period..!?!?

Hi so I apologize but I'm just confused.. last insemination was Nov. 25th and I was suppose to have my period Dec. 5th. So I took a test on Dec. 11th and it was negative not even a faint line. It's Dec 13th and I still haven't started. So should I take another test or just count this as a late (late) period.? Appreciate any advice.!!