Welcome, sorry about your little guy :(
Is his stomach bloated any at all? Is there a way you could put a picture on here for us to see?
If he isn't bloated, and just having issues swimming, then you don't have to worry about fasting, nor trying the pea method. If he is bloated then luckily, it's the same treatment for SBD :)
You already fasted him, so go ahead and feed him half of what you normally do, so he can get some nutrition going. Don't feed him any peas, as they can't digest them properly, and it can cause blockage as well. People use it in hopes to "push" out whatever is in their system because the body is trying to reject the pea.
If you have a smaller container, even a soap residue-free tupperware, go ahead and place him in that and float in his home tank to keep him warm.
2 teaspoons of Epsom Salt (can be purchased rather cheaply at most places with a pharmacy, such as Walmart) per gallon. You will want to do daily 100% water changes to his QT container while he is in the treatment. It shouldn't last more then 10 days, but go ahead and keep him in treatment for a day or two past the last time you saw he had swimming issues.
To make water changes easier, use a water gallon jug to pre-dissolve the salt in it (pre-dissolve prior to adding it in as it is), with your regular water conditioner and use that to do the daily water changes. Just fill up the jug each time you empty it. It will make the water change process easier and faster for you.
What are you feeding him, and how much/often?
How often do you do water changes, and how much?