A possible death in the family

My male fantail goldfish keeps floating upside down. He will do it for a few minutes then go swim a while and then float to the top upside down again. Generally, this is not a good sign. I am feeding them peas to try to unconstipate them. That is usually what causes that but I think I am probably too late. I have had that fish longer than I had my last husband. I sure won't cry when it dies but I will feel sadness at it's passing.

Edit: He made it through the night so I am more optimistic. He still floats upside down at the top some times but less often.

Edit: The peas seem to have worked. He quit floating upside and swims normally now.