I guess every woman is built differently. I could feel the top of my uterus at 12/13 weeks, and even then I had to press into my pelvic area to feel it. Yet at 15 weeks a stranger asked me if I was pregnant At 8 weeks the baby is only about 1.5 cm and at 10 weeks about 3 cm...Whereas by 13 the baby's about 7.5 cm!
Yeah, I know alot of it is water retention, but my stomacvh was close to flat last month. I've gained like 5 lbs since march, and I'm 6'1, so its not like I gain weight all in my stomach, it usually spreads out on me.
Heres a pic.