What is going on with my body?

Okay so my period is about a day and a half late ... I don't think im pregnant I haven't had sex and my boyfriend is 100% sure he didn't finger me with any precum on his fingers. He is trying to get me to calm down but its so hard .. What could be delaying my period? Could I be pregnant? I have my normal PMS symptom which is only my right boob that is sore. I'm 17, please help