Period?

My period was due today and its not here... i range from 24-33 days and today is day 31. I havent done anything except mess around and got fingered but that is it... i had bad cramps about 3 days ago in the morning when i woke up and they went away and i haven't had them since..im not pregnant right? I mean there was no cum involved. And can someone explain and the myths about if cum touches air it dies and stuff? It would be really helpful since my school doesnt teach students anything about this kind of stuff