Fatigue!??Anyone?

So I have sorta irregular periods so I always make sure I take note of when it starts and ends... according to my notes and this app I was due for a period yesterday and there was nothing....about 2 weeks leading up to that I had no cramping (which is what I usually get before period) I always had no lower back pain.but starting about 4 days leading up to when my period was suppose to start And up until now I’m experiencing extreme fatigue!!!!,which is very very New for me and I never get this ever even before a period..any suggestions??