Distended stomach is likely going to be due to overeating and/or gas. When I was first starting out, people drilled it into my head that I had to eat eat and eat to gain mass but no one really stopped to explain how to figure out my actual energy requirements and how to plan my diet accordingly. I had to figure that out the hard way much like yourself, when my stomach started to appear to gain mass faster than anything else. You need to learn how to estimate your lean body mass and plan a diet that fits your needs. Without any more info there's not much anyone can tell you, but I would suggest heading over to the Nutrition section of the forum and starting there.