1st of all this is the wrong board to post on, this belongs under goldfish, general or beginner.
Goldfish should not be kept in that small of an area. Each goldfish requires at least 20 gallons. here is a good site for goldfish and bowls
http://www.peteducation.com/article....articleid=2650
I am thinking that because of the poor water quality your fish has developed a disease, of what kind Im not sure, the pros will have to answer this one.
It may be too late to save him and if you intend to it is best to set up a bigger tank right away for him