Should I Be concerned?

My girlfriend is 4 days late on her period. We had sex 3 times in the last month, none of which was when she was ovulating. We have used condoms everytime, and I have never finished. I am seriously stressed, should I be concerned. She was 5 days late last cycle but I am nervous she could be pregnant. She has been super stressed the last few weeks and I’m trying to not stress her out further. Please help!