Mr. Fishy is all of the suddent fat!

Question
So I asked a question earlier about my betta with velvet, and you said that he showed signs of early velvet. So I did what you said to do and I changed his water, disinfected everything, removed his filter, turned off his light, and added medicine.
I had mr. Fishy in my room in a smaller fish bowl while I cleaned everything. Before I left he was perfectly fine and seemed happy and curious about his location. When I came back I didn't really look at him I just put him back in his tank then put like three pellets of food in there. I cleaned up all the fish equipment and then came back to look at mr.fishy. When I came back, BOOM! Mr. Fishys tummy was huge! Almost as if he was pregnet.
Obviously male betta can not get pregnet expecailly when he's the only betta I own.
Plus, he was taking alot of "breaths" so maybe he's just puffing himself up with air? Or is he bloated from the food I fed him? Or did he just become fat real quick and he needs to be on a diet?
Please help me with mr. Fishy. I don't want him to be in any discomfort and I want him to be that happy betta he used to be that would greet me everyday!

Answer
Katy,

If you disinfected his tank and everything in it with any kind of chemical. REMOVE HIM FROM THAT TANK IMMEDIATELY. Take everything, including the tank. and rinse it very very well with hot water. As hot as you can get it. Then let it air dry outside in the sun. When it is dry, and you can smell anything on the this stuff you are drying, leave it out in the sun longer. Only bring everything back in when you no longer smell any chemical or an other odor. He needs to be put in clean fresh water that has been condition, but not in his tank. Use a bucket or a big bowl. He is likely being poisoned but whatever the tank was disinfected with. The reason he is breathing hard is because he can't breath in the water. If you used a household chemical, then chances are everything wasn't rinsed out enough. Keep the heater on, and ad an air stone in the tank with him going vigorously. Have him in 3 to 4 inches of water so he can get to the surface for air. Keep whatever you put him in plain. No gravel, no plants, nothing but him and his air stone. The heater takes oxygen out of the water so the air stone replenishes the water.

Leave him where you have him and let me know how he is doing in 24 hours or sooner if other problems arise.

I will wait to hear how he is doing.