Late Period and getting worried

So i'm a day or two late (i usually get my period every 28/29 days) and i'm getting pretty worried. I had my period on July 1-7 then had protected sex(with safe pullout and there was no damage on the condom) on the 9th and then my boyfriend went on vacation so we haven't had sex even until today. I've been cramping with back aches which show signs of a period but also pregnancy. I know and trust that nothing will happen but i'm just scared because my period is late. Does anyone know reasons why it's late? I have no discharge as of now so i'm super dry. Could i just have ovulated late?