What can make your period late?

I'm only one day late for my period but I'm stressed out about it. I haven't had sex for 3 months and I've had all my periods up so there's no reason to be stressed about being a day late. I'm a sophomore in high school and I participate in a lot of groups at school and I take 4 honors classes so I'm stressed quite often. Could stress be why I'm late? Someone give me advice please.