HELP?!

I had sex exactly a week ago (with a condom and we checked to make sure it didn’t break) yet my period is due tomorrow and I don’t see any of my normal symptoms, most obvious being sore boobs. I just have a headache, I feel tired, and slightly nauseated, could I be pregnant?? It just doesn’t make sense to me, please help!

Also! I had a 3 hour drive in the sun with no ac yesterday, could it be that I’m dehydrated?