Late Periods

I am 40 years old, my cycle has always been pretty regular, 18 months ago I had an 8 day late period but, has returned to normal since. I was due for my period now 7 days ago and I am starting to worry quite a bit (constantly checking, losing sleep, bad health anxety that something is wrong bc this is so uncommon for me). Additionally, I have done two pregnancy tests (negative) but, have no idea what is going on. Is this a common age where period irregularities start to occur? It is starting to stress me out as I don't have any other PMS symptoms indiciating it is on its way and I am stressing myself out. Can anyone share their experiences with late periods and the start or preimenopause/menopause so I can calm down.