I'm at week 20 and my belly is so small, like I just ate well and that…

I'm at week 20 and my belly is so small, like I just ate well and that's it. Looking at pictures from week 20, you can clearly see the belly. In theory, the baby should be about 20 centimeters by week 20. I looked and think that's already pretty good. The belly should be visible now (and I pull up my shirt so it looks like I just ate well, like my belly always did before pregnancy).