Sounds like he has swim bladder disorder (SBD). Its not fatal or contagious. Do you have any Epsom salt on hand (unscented)? If so had that to the tank, if not go buy some as soon as you can.
Fast him for a few days. Also try to make him flare by bringing a mirror up to his tank or use an exercise mirror if you have one. DO NOT FEED HIM A PEA, i know if you do a research about SBD they say to feed them a pea. Don't do it.
Also what are you feeding him? blood worms are going to make him bloated easily. try some high quality pellets
Fast him for a few days. Also try to make him flare by bringing a mirror up to his tank or use an exercise mirror if you have one. DO NOT FEED HIM A PEA, i know if you do a research about SBD they say to feed them a pea. Don't do it.
Also what are you feeding him? blood worms are going to make him bloated easily. try some high quality pellets