When you're 14, never actually have sexual inner coarse but you're period is late; cause?

so im almost 15, but i've have my period since i was a little over 12, and my period has always been right on time. as of today my period is 3 days late me and my boyfriend do have sexual relations but never have had actual sex. we've came extremely close once, without any protection but stopped because we didn't have any. and have not attempted since and have decided to wait. and ideas of why my period is late? im worried and neither of us know what to do.