How to get rid of my distended abdomen?

Before I start, im not really that fat. My face, bum and arms and legs and chest are all just normal-verging on slim. However my belly sticks out more than most people's do. It looks odd to have a belly sticking out when I'm so slim. I do not have much fat under my skin there, its just that my visceria (ie my interal organs) inside my belly do not seem to be getting held tightly in place. I am consious that my belly distends and often hold my belly inwards. Before I gave up smoking I had a flat stomach, but when I gave up a year and a half ago I put on weight. I have lost the fat I put on, but I'm left with a belly what sticks out. I even heard someone say pregnant man to their friend and it upset me a bit. I eat at least 5 fruit and vege a day, plenty of protein and I am otherwise very fit and healthy. What can I do about my tummy?