I’m 3 days late and negative test

Jessica • Mummy to a 5 year old💙and 5 angel babies👣 Second baby born 28.10.20💙 Baby no.3 due 26th March 2023

I’ve all ways had an exact period 28 day cycle every month, I’m worried but I know I’m not pregnant as it’s negative has anyone been late before and maybe knew why?