Late period

I am 9 month postpartum. I have had regular-ish periods month 2 after the baby. This month I am 9 days late on my period. I have taken 3 tests that showed negative. I have never in my life had a period that “skipped”. With my baby I showed a strong positive when I was 3 days late on my period. I will be testing again today and if I haven’t started I will go get tested by a doctor. Just curious if this has happened for anyone where they truly weren’t pregnant and were very late. Google just spews scary information that says well you could be pregnant/dying/or just fine! So just looking for some support from others. Thank you.