Protected Sex 2 Days before period was due, now a week late

Ok, my girlfriend and I had protected sex 2 days before her period was due. I used a condom(durex extra safe), I made sure i put it on before any contact, it didnt slip off, it didnt break, as soon as i came i pulled out, so i was still hard when i pulled out, I then filled the condom with water to check for breakages or anything and there were none and everything seemed fine with it. She was supposed to start her period exactly a week ago, 2 days after we had intercourse, but she hasnt, and we're both really worried. I read That 2 days before a period its almost impossible to get pregnant as a woman is at her least fertile. I also read stress can lead to late periods, and my girlfriend said she has been quite stressed and upset as a family member passed away a few months ago, and she was also sexually assulted as a child and she has said shes been thinking about that alot recently, so could this be a cause of her being late? Im trying to think of how she could be pregnant, and it seems the only way is if some how some sperm got through the condom, but how could this happen if the condom didnt break? Is there any way she could be pregnant? Please can someone help, we're both so scared, we're really terrified. Shes 17 and Im 16 (only a months difference though) please can someone help us, is she pregnant? Is it something else? Help :(