Hi, Yeah he seems like he has swim bladder which is mainly caused by over feeding, fancy goldfish are particulary prone to this condition. December is a long time for him to have been floating!   Your fish must have really been suffering!
Feeding your goldfish peas is the best solution, have you tried this? Thaw the pea, de-shell it and feed him it in halves. Only one or two should be needed. Don't worry if he doesn't eat it right away, take it out and try again later he should eat it in the end. Keep your chin up if you try this is should work.
Hope this has helped!

 thank you Karma, I have a 40 gallon that he share with two black moore,  but the moores are perfectly fine, I just moved Dinn, the oranda today to a 3 gallon and fed him the green peas he did not eat a lot. This tank is heated 80 degrees, they said this should help with bacteria, I am keeping my fingers cross.

Please keep the poor thing in a proper container, do you have any large plastic tub for now?
It might help keeping the water level lower than usual, about half-way to the top as the pressure from the water would be relieved. Also, you've probably been feeding your fish all wrong, which is what caused the illness. And... most of all I wonder why on earth you let it suffer like this for 3 long months?!

Either way, go to the pharmacy please and buy some epsom salts, add 1/4th of a teaspoon per gallon of water to whatever container you keep the oranda in. Do not feed him/her for a few days and then slowly start off with peas, squash and some live foods.