First what temperature is your water?

If he has been eating unfamiliar food or too much food he could be constipated and especially if he is not in the range of 80 degrees to 82 degrees Fahrenheit in his tank. they do not take to changes in foods very well especially when they are stressed from any other changes. Please do not feed him and try to get his temperature up to about 82 degrees slowly if you can. They really need to be treated like tropical fish and have heated tanks.

Then if you have not seen any pooing in the next few hours get a frozen pea and put it on a saucer in the microwave for 20 seconds with NO water on HIGH setting. It will not cook the pea just defrost it. Then peel the outer skin off and take one of the halves you find inside and cut tiny chunks about half the size of his eye and try giving him one or two at a time three times a day for the next few days with no fish food at all until he is feeling better.

I would say that he sounds like he is combination ... overfed and different foods constipated and developing a swimbladder problem due to the constipation. If he is not in a good temperature he may not make it. Fish are cold blooded and when the temperature of the water drops they cannot digest their food properly and if he was already compromised he will be harder to treat. Somehow you need to get his water heated and yet you cannot do it in that bowl. He has to be back in the tank. (is the tank heated?)

Then when we get the fish to respond to the peas and swimming or trying to again, we can deal with the meds for the other problems but the constipation will kill him faster than any of the other problems he has right now.

Probably the major cause of death in tank held bettas is too much food and not warm enough water. They really need to be kept 78 to 80 degrees steady temperature and the food given needs to be very small amounts. The fish's stomach is only the size of its eye and they do not need a lot of food. Most foods expand in the stomach so I always soak pellets or any dried food so that it will not expand in their stomach. They are little piggies and will eat until the food is gone and that is why they need strict control of their owners.

I wish I had a better answer for you but this is the way bettas are sometimes and they have some of the most touchy digestive systems of fish.

Please do let us know if there is any change.

Rose