Why is my stomach so disporportionate?

I am pretty slender and work out alot, usually 5-6 days a week running, ab work, weight ect. But no matter what I do my stomach is huge! it has some flab, but more so when I don't hold it in in front of the mirror it just sticks out! I don't know what to do bec I am already in very good shape. I'm sure losing weight would help a bit, but is this just my shape? could I eventually get lipo or is that the way my bodys structure is??? could it be something medical??