Everyone is different so it will vary, I'm a size 10 didn't exercise and had a bit of a belly before pregnancy but not massive and I started to show a bit by 13 or so weeks, that was probably bloat though! Around 18 weeks it was hard to hide though! Now I feel like a bloated beached whale at 25 weeks!
Saw my baby bump when I was 20weeks. :)
I was 25 weeks. But im 5'10" and my son tucked into my back. So it took a while.
I didn't start showing till I was 20 weeks