Late period causes?

So my period is 23 days late? If I'm working it out right.

I've not had one since Christmas time, got a pretty typical diet for a twenty years old and there's been no major stress? My mood can be kinda up and down due to stress and mental health but nothing bad enough to miss a period. I was slightly late in October-November time but that was only by around 5 days.

I shouldn't be pregnant since I'm both a virgin and tend to prefer girls but I have been in situations where something could have happened even though I don't think it has.

It's pretty dumb but it's stressing me out not knowing what it is. It's not medication because in the three years I've been on it, Ivs not had an issue, I haven't taken birth control in over a year either.