Depends on a lot of things, fitness level, shape of your chest, shape of your spine, if organs are enlarged or not, if you're on cortisol type stuff, and maybe most of all if your digestive issues are severe or mild.
But eating your enzymes right, lots of fiber and trying to prevent obstipation (as far as you can control it) certainly helps.
Other then that, getting the rest of your body muscular makes your stomach relatively smaller and better in proportion. And as I read you got into bodybuilding you're on the right track.
Personally ontop of that I like to do vacuum excercises a couple times a week and it might just be in my head but I like to think it helps too, atleast it feels good. (well atleast it'll help you to suck it in when a pretty lady walks by, mhm.)
And the best thing is not to worry about it.