It can be an infection in the abdominal area cos he does not poop.

If he swells up , im sorry to say i think you have to humanly euthanize him.

If you have a smaller tank to put him in by himself that would be great , make sure its the same temperature and water from the bigger tank , if he has infection in the abdomen the risk for dying is big , im sorry =/

Buy some Nifurpirinol thats a good medicine for abdominal problems =)

I hope it helped =)

Thanks Sofie for responding.

Im not quite sure its an abdominal problem because there isnt any bloating or swelling on the abdominal area. I have been keeping a close eye on him.

It could be Oodinium. It is harder to diagnose than Ick. What about his breating? Is he breathing normally or unusually fast? If he is he might have parasites in his gills. Are they red an a little swollen? Oodinium often attachs the gills first and later spread all over the fish. Nitrite-poisoning also causes these symptoms. Both parasites and nitrite irritates and can cause iching gills. I have come across these problems and my fish didn´t enjoy eating and became very picky. I think that  they, as well as sore gills get a sore throat. If he has trouble breathing I recommend checking for nitrite and in case of a high value to make a fairly large waterchange. If not, or if the sympthoms remain I agree with Sofia - remove the gourami from the other fish in order to protect them from getting infected.

About Oodinium -> http://freshaquarium.about.com/cs/disease/p/velvet.htm

Adding some…

Nitrite poisoning
http://freshaquarium.about.com/cs/disease/p/nitritepoison.htm

Ammonia poisoning
http://freshaquarium.about.com/cs/disease/p/ammoniapoison.htm

fun with someone who speaks English on this page you must excuse my English is not so good I'm only 12th. It sounds like an infection blue gouramis can be a bit lazy, but occasionally it will pass anyway with my. Hope he gets better.