Welcome to FishLore

I'm really sorry that your fish is worrying you.
What are your readings for
ammonia,
nitrite and
nitrate?
Tank size? How many and what kind of tank mates?
He's really bloated. Are the scales raised when viewed from the top?
It might be a good idea to put him in a quartentine tank and try fasting him for a day or so then feed him to tiny pinch of thawed frozen shelled pea. If it's constipation, that should help a bit. How long has he been this way?
If you could fill in your aquarium info, it would be helpful to the other members. It's found under My Settings on the top left.