My Girlfriend And I Had Unprotected Sex Last Week And

My girlfriend and i had unprotected sex last week and 2 weeks ago, after 3 months without having sex. She told me today she did not get her period but this has happened 2 times before last year and she still got it but late but she turned out not pregnant. Is it possible that she is pregnant even though i know i didnt ejaculate in her or is her period is late cause we didnt have sex for 3 months and her period is off schedule?