How fast did your stomach grow/is it growing with your pregnancy, esp. a second one?

Hey hun! I am 15 weeks, just went to the doc and everything is fine, but my stomach isnt any bigger.. maybe its because i am tall 5'7 or maybe its my built.. i havent gained weight either.. like one pound only (i didnt have nausea so i ate well) Baby is doing fine so i think thats the only thing that matters. Good luck hun*