3 days late

Ok so I haven’t had sex since my last period but I let my boyfriend go in raw for literally .2 second n he wasn’t even all the way in because we were interrupted. And he didn’t cum so it couldn’t be that. But I was supposed to start 3 days ago according to eve but I haven’t started. So I’m scared but ik I’m not pregnant so like is the time just changing? Like I will just get it later in the month or??? Pls help