Am 12 days late for my period also had some light spotting 2 weeks ago and it lasted 2 days this is very strange for me as I've always had regular periods but I've tested with home pregnancy test and they all say negative

And the million dollar question is... what kind of birth control if any are you using??
Periods can be different, no matter how regular they were.
Women who get periods can always get pregnant, no matter what birth control they use - it's just that the pill, patch, and IUD are way way down the list, and withdrawal is way at the top, and condoms aren't too far from the top.

I'm not using any birth control as we are trying for a baby

You asked this under Child and Teen Health.
You are a teen deliberately trying for a baby?