how do i end his suffering??

[Alysser]

Yeah, try putting him near another betta! Hopefully, that will help. There is medicines. But you have to get the sickness first.

[Flatcoatluver]

I tried to some reserch and the close i could find is Swim Bladder Disease. I contacted the person who wrote that page and I asked them if my betta could have it and described what is going on.