Sometimes it takes a while for this to clear up... not just a few days but even several weeks. But you're doing fine already from the sound of this, Annie. Keep up the good work here.. and just keep the water clean, that's most important. You could let him go a day or two (even three) without any food at all, then resume feeding peas again very slowly. You want to help clear out the food that hasn't passed through yet, rather than feeding a lot of peas too soon. Really, it just takes time. I know the fish looks sad and miserable like that, but the isolation and peace you're already providing is what he needs most right now. There's really not very much else you can do to treat this. It's more a matter of waiting it out and not filling him up inside with more food.
I'm not exactly sure what you meant by saying he looks twisted up. Is he floating at the top on his side or upside-down? Or mostly sinking at the bottom? Make sure the aeration in the tank is good so the oxygen level is high. That makes breathing easier and less stressful. A little aquarium salt in the water (dosage on the package) may be soothing for him.