Im 15 weeks today, Not showing yet and havent put on any weight?

Im worried - Im 15 weeks today and havent put on any weight. This is my fourth child and I can feel movements every now and then BUT shouldnt i be showing by now. My tummy just feels soft not hard. I weight 63 kgs and im worried that the baby isnt growing or something. Or is this normal not to be showing yet. I put on alot of wieght with the other three pregnancies and last year lost the weight finally. Now Im pregnant and i feel pregnant but dont look it. Can anyone offer any advice or reure me?