A lot of factors need to be considered here. Your age, your muscle tone, the kind of activities you do. I didn't look pregnant at all up to 6 th month and suddenly in the 7 th month onwards it looked like I was carrying twins. I walked like a penguin. So do not stress. Be positive. Your scan results may help you understand baby development better with the help of your doctor.

It's normal, only by 7 months bump will be visible.

Its normal because during 16 week baby is not too much big