I'm not growing

Ch
I am 13 weeks pregnant and I feel like I have nothing to show for it. My stomach is still flat with no bump. When I lay down my stomach is somewhat firm in between my belly button and vagina but I'm really scared that I'm not growing properly.
I had a scan at 12+2 weeks and they said the baby is perfect size but I feel like I should be showing abit more.
I understand that everyone is different and I did read up that most people start showing by week 14-16. But I have a friend who is 18 weeks and she is huge. 
Is anyone else in the same boat? Like they are really impatient when it comes to growing?