i am 19 weeks tomorrow and really only started showing about 2 weeks ago. I could tell myself, with no clothes on, but dressed (not in skin-tight stuff, obviously) you couldn't really see anything until about a week ago.
I was surfing the web looking for bump pix becuase I thought it was too small! That was quite reassuring, becuase there was a big variety of sizes.
However, the bump seems to have grown quite quickly in 2 weeks! Although obviously i want the baby to be the right size and have plenty of room in there, I am quite pleased to have remained usual-size for quite a long time, I'm sure being huge gets tiring and wearing after a while!