Oh really? Thank you for the advice, hopefully that will help someAll you've been feeding him is blood worms?
Bettas love frozen foods, but they must be fed sparingly. Blood worms are one food that can cause issues if fed too much, one of those problems being bloat. You need to get him on a pellet food specific for bettas. I'd fast him for a couple days first, then try getting him to eat the pellets.
That sounds like a good idea, but should I wait a bit or do it right away? Would it stress him out too much right now?