Worried my bump is too small? 20 weeks?😞

People keep saying to me how on earth can I be 20 weeks?! I was very very skinny before, never unhealthy... I’m just one of those people that can eat anything and have always stayed the same size my whole life..... I’m really worried by baby is too small... I see other 20 week bumps and I’m terrified😞

Here’s one from 5 weeks...

One from 18....