when did you ladies begin "showing" ?

This is my third pregnancy and in 8 weeks 4 days with twins! Yesterday and today I've noticed my belly protruding (not like a perfect she's obviously pregnant belly) but it's getting much harder at the bottom of my belly and I have a pooch that sticks out where I never have before. I've even noticed people looking st it (we just announced the other day) I feel like I'm in the "fat stage" of pregnant were people are trying to determine if I've just got extra weight in my midsection or a baby in there! lol I begin showing at 24 weeks with my first, and 16 weeks with my second, 8 just seems too soon even for twins! Am I the only one? Or is this common?