Freaking out

Hi, my gf's period was due today and it still hasn't came and I am freaking out.  We had sex only on her non- fertile days and always use a condom (no break/slip) .  I'm terrified , she is fine tho, she has had no symptoms besides light cramps that indicate to her that her period is coming soon.   But I really am scared, does anyone have advice?   Could she be pregnant based on our BC that we used