With my first daughter, I was 5:3 and about 105 pounds before I got pregnant. I started showing with her at around 18 weeks. And it didn't look like a pregnant belly it just looked like a pooch. At about 25 weeks it started looking more like a pregnant belly.
With this pregnancy, I was 5:3 tall and 95 pounds before I got pregnant. (yeah I lost all of previous baby weight, then some!)
i started showing at about 10 weeks! It was just a little pooch but it was still there. I started looking actually pregnant around 18 weeks. Now i'm 26 weeks and its very obvious i'm pregnant. My last appointment was monday and I weighed 108 so i've gained 13 pounds so far. Seems like it should be more than that