how long you have him? I am just curious if he is old. I have a betta (2.5 y old) that never was bloated before. All of a sudden he got bloated ,was bloated for about 10 days. I fed him frozen daphnia, small meals. Then i decide to give him Epsom . He got back to normal but still get a little bloated easily. So i am trying to feed him small meals and frozen daphnia sometimes.
Do only full water changes , don't even do 50% at all. The less water movement,the better it is.
Try to feed one pellet in the morning and one at night. Frozen daphnia would really help.
Just like Aquatail said see if he will not get better with small meals then try Epsom . But i would give him more time. It is a good sign that his poo is normal color .
Keep us updated please, good luck!