First of all, what brand of food do you feed him/her? bloodworms can be quite bloating, so we should find some sort of pelleted food that he likes. Also, to get him to eat the pellets, you can try fasting him. (in case you don't already know, fasting is not feeding the fish for a certain amount of time) fast him for three days, then try feeding the pellets. If he still won't eat them, then fast for another three days. If he still
doesn't go for it, try new life spectrum
Betta pellets. (if you haven't already) new life spectrum Betta food is pre-soaked in garlic juice, which makes the food much more appealing to the fish, plus you don't have to do it yourself if the fish isn't eating.