Preggo???

So here's the story: I'm 18 and my bf and I had sex this last Saturday. We used protection and triple checked for no leaks or holes- no chance for a mistake right? My period was supposed to come on Monday or Tuesday. It's Thursday now and I feel nothing and no sign of it coming. Most times my periods are on the late side, but I'm making myself literally sick worrying about this. I don't know what to do. My bf says that there's no way and so do all my friends.. but what do I do if I'm pregnant? My parents can't know and I can't have a baby. I'm about to go to college. Any help is appreciated- I'm very scared and alone right now.