I didn't show with my first until I was 7 months also. Now I'm pregnant with my 2nd and I started showing at 8 weeks lol. Now I'm 19 weeks and have a little basket ball lol.
With my first I didn't start showing til I was 7 months
I'm 20 weeks with a boy too & I'm not showing either. He is very very low, but I do feel him moving around.
I'm 21 weeks and not showing yet. My doc said it is ok. It really depend on your body.