I've had my betta fish for a few weeks now and within the past week he's started eating the food I've bought for him (Betta Bio-Gold). Today I noticed him acting a bit irratically so I decided I'd feed him to see if that would help. He attacked his food like he was starving or something (which I know he's not) then when he finished I decided to change out some of the water in his tank. After doing that, I watched him closely and realized he was acting pretty odd for how he normally does. He physically looks bloated in what I believe is his stomach and then also in his swim blatter. Look here for diagram:
He also cannot swim properly because everytime he tries to swim to the bottom of his tank, he just floats right back up to the surface. Like he cannot sink. I don't get it. I've never seen him do this before and I researched it a little bit but I couldn't find someone with the exact same symtoms as his. I thought maybe it was constipation, so I'm going to try and not feed him for the next or two to see if that helps. PLEASE let me know if you know what this is or have any suggestions to help my little guy! Thanks so much!