Any Ideas?

For the last few days my tummy all over has been really hard. It doesn39t hurt or anything. It39s hard like around my rib cage all the way to my lower stomach. I really don39t think it could be gas or something like that because it wouldn39t be hard all over or would it? The hardness feels kinda like I swallowed a whole watermelon. I know it sounds weird but it39s the only way to describe it.. Well any ideas on why it39s hard like this?