I didn't start showing till about 22 or 23 weeks so don't worry :)
Thats perfectly fine. I didnt find out i was pregnant until i was 19 weeks. My stomach was still as flat as the walls. Everyones different
I don't start showing until 20 weeks but every woman is different. It could be from when the baby implant its self to the uterus it could have been low or another one is that the baby sits towards the back.