Testing BFN and no period

I was due on my period Wednesday I have tested twice now and still no faint line. I am panicking as the internet says one day after missed period pregnancy tests are 100% accurate.

So if I am not pregnant (gutted if I am not) where is my period.

This then got me googling more and panicking there is something else wrong.

When did ppl get a positive result after a missed period?