Help!

madison • 22
Hi ladies :)
My period always comes exactly 20 or 21 days after my last period. But so far this month it's been 23 and still nothing and no symptoms of my period coming. I haven't had vaginal sex any time recently but I've had anal several times. But I also moved into a college dorm room (for the first time ever) over an hour away from my house and am taking 17 credit hours. So what do you guys think is going on?