Distended stomach, please help?

I am quite fit and healthy, I exercise practically everyday (mostly kickboxing, walking, and strength training). I also try my best to make sure I eat very healthy. I'm lactose intolerant I'm not much for meat/fish but I make sure to get all my nutrients in my meals. I'm 5'8" and weigh around 120 (it varies from 120 to 123 from time to time). I have a pretty strong core and I know there is still a small amount of fat around my stomach but my stomach always looks HUGE. I have some GI problems but I'm on medicine for that and my stomach doesn't hurt or feel bloated. Is there something I could be doing wrong or something that I'm not doing to fix this?