5 days after missed period - negative pregnancy tests

Hi! New to this group AND just started TTC. My period has always been really regular - 26 or 27 days like clockwork - so I was really excited when I was late this month. It’s currently day 31 (so, 4 or 5 days late), but I’ve now taken 3 negative pregnancy tests. Doctor says it’s possible I just don’t have enough HCG built up yet, or I just missed one of the first periods I’ve ever missed since I started at 11. I’m also freaked as I just turned 40 this month - so if I really just missed this period feels like an extra cruel joke from the universe.

Anyone experience a “negative” after 5 days late that turned into a “positive”? Should I keep my hopes up or chalk this up to a fluke?