late period !

Hello ! 
I've recently become sexually active and I am having the usual stress about pregnancy. I'm on Yaz, and we used a condom the first time but after that not again. 
Tomorrow will be my last day on the sugar pill and then I start a new pack, but my period hasn't come yet ! 
Do I start the new pack anyway ? If I do, will my period still come if it's late ? 
Your advice will be a great help as I'm stressing out.