Since you had vaginal sex- there is a chance of pregnancy. Your biggest risk would be the unprotected sex, since the pre-ejaculatory fluids that can come out through out having sex, can contain sperm. Condoms reduce the risk of pregnancy significantly, but don't remove the risk entirely.
Since you are late- I'd recommend getting a test to check. Late periods can be caused by many things, so it could be stress or just changes in your body, but it's best to test to be sure.
Good luck and let us know how you are doing.