Im wondering if shes late this month or what are the chances of her being pregnant

My girlfriend and i had intercourse a month ago with a condom but i ejaculated in the condom and continued. She got her period on time that month. This month me and her had protected intercourse a couple of times but 2 days before her period was due, we had unprotected sex for less then 5 seconds. Now her period is 3 days late. She mentions that her breast didnt get tender a day before her period was due which is unusual for her. She had random backaches a few days ago but now it has stopped. She is also experience no other pregnant symthoms. She also sometimes have irregular periods so i dont know. Im wondering if shes late this month or what are the chances of her being pregnant