Has your period ever been late and you knew you weren’t pregnant?

What ended up being the cause?

I know certain things like weight gain/loss, birth control, etc can affect your period.

My periods are always Very regular and suddenly mine is 5 days late. I haven’t experienced any of the changes listed above or anything especially stressful.. I can’t think of anything that would cause this.

I am going to the clinic tomorrow to get my blood checked (possible hormone thing ?) but I was wondering if this has happened to any of you, and if so, what it ended up being?