My GF had unwanted 72 & still she din get her period!!

My GF had unwanted 72 & still she din get her period!! Is she pregnant??

Actually she had her last period on 10th Sep to 15th Sep, then we had unsafe sex on 19th & she had unwanted 72 on 20th itself... but still now she din get her period!!!

Is she would be pregnant???? 

please someone help me...