Have you ever just 'known' you're pregnant?

Kay • 👸🏼💖 Girl - 2017 , 👰🏼❤Wife - 2018 , 👶🏼💙Boy 2021

Its 8 days until my expected period and i feel like i know I'm pregnant. Of course i could be completely wrong but after 2 children i know that feeling in the uterus.

What is the earliest i could test from everyone's experience?

I have a 4yr old and a 5 month old 🙈 both i didnt test until after missed period previously.