Always on time or early... 4 DAYS LATE! Need advice!

I can count on three fingers how many times my period has been late in my 29 years and every time it’s only been by 1 day...

I am currently 4 days late, but tests are showing negative.

What should I do? I don’t want to keep wasting $ on tests, but if there’s something else going on, I need to find out that too.