Thank you for waiting. Your betta is very sick, and it may be too late to save him, but we can try. It sounds like he has more than one illness. Start with a water change. Use water the same temperature as what is in the bowl, and taht has been dechlorinated. I recommend that you add aquarium salt (available in the pet store) at a rate of 1 teaspoon per gallon of water. That helps fish deal with any kind of stress, eliminates some external parasites, and improves water quality. You can also use some Melafix according to directions on the bottle. Melafix is sold in most pet stores.
The whitish growth is either a fungus or columnaris. Both the salt and Melafix can help with that, if it isn't too advanced. It sound slike your betta is also suffering from swim bladder disorder. The salt can help with that. The other step to take for it is to feed him nothing but thawed out and peeled frozen peas for a few days. You may have to hold them right in front of of his face.
In summary, do a water change, add aquarium salt, feed peas, and medicate with Melafix. If you have more questions, let me know in a REPLY. I hope your betta will be able to recover.
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