Right now, I would keep the water extremely clean with plenty of water changes. You can add some Melafix and Primafix, you could also go with a stronger antibiotic but if it is the swim bladder it's very hard to cure. I would use Paragon II by Aquatronics. Do you have a quarantine tank? If so I would definitely put him i there.
If it's not the swim bladder it does sound like some sort of bacterial infection and an antibiotic is needed. I would stop feeding your fish for a few days and start feeding him some peas. You can also raise the temp a bit and add some sort of extra oxygen (bubble wall, power head, ect).