Whoa, that sounds like serious water quality issue. When was the last time you did a water change? Do what Nathan says and make sure the temp is around 86-88 F too. You need to do some serous "preventive action" here to try and make sure this does not develop into something serious.
The only time I had a fish develop a condition like what you describe, it later developed into dropsy; it was due to my keeping a 15 inch RTG at my dad's for a long time; the water did not get changed, the filter did not get changed, and the uneaten food did not get removed. My dad just didn't know how to care for aros.
Good luck with it. Take some photos of the fish if you can and post them.