I started "showing" at 8 weeks with my second pregnancy too, but chalked it up to more likely being bloated. Baby and uterus aren't large enough at that point to be pushing out on your belly. A noticable bump wasn't until about 12 weeks unlike the 16-18 weeks with my first.
I’m on my third and had a “blump” by 6 weeks as big as 13 weeks with my second. It’s only gotten bigger. And I was at the smallest/fittest I’ve ever been. I’m also only 5’ so I’ve always shown fast due to a short torso.
It is common to show earlier. I showed by 3 months with my second and for my third I felt like I "looked pregnant" which is what made me take a test and of course it was positive. I was about 7 weeks along by then and always have had irregular periods which is why i wasnt even worried when my period didnt ahow up lol 🫠🫠