Awww Sakura! He looks exactly like Azule (my special boy) did when i brought him home lol minus the blue lip stick my boy sports! It sounds like he has the same problem as well.
If his apatite is ANYTHING like Azule's, he will ALWAYS beg for more and more food.
a while back i went and got a betta for free, becuse he was bounding around at the bottum of a large community tank, and he had no fins. He has a problem with his back, and cant swim horizontal, he scoots around with his nose twords the top of the tank and hops around on his butt. I have him in about 5-6 inches of water with a betta hammock, sand ( i recomend sand if this little guy scoots, becuse the rocks would argavate his tummy), and a little heater. He eats anything and everything i give him, because he needs the protein to regrow his fins. I do 90% water changes every other day, but thats it just because his fins are regrowing and still sensitive. I feed him cooked egg yolk (loves!), Mosquito larvae (OMG!), pellets and he will even eat flakes. He flares at females and males alike. He is a generally happy fish, who NEVER runs out of energy. lol
Oh, okay, if this little guy doesn't start swimming in a week or two he might be just like Azule. If that's the case, it's good to know it's not a death sentence and that he can have a happy life. If he is like that, I know how to set up his pemanent home, too, 'cause he can't live in a Gladware for the rest of his life. Thanks, GunsABlazin, this does help me.
Try some Frozen Brine shrimp too if you can get them. They did wonders to my fish's color and energy. I give them 5 every other day and the improvement I've seen is amazing. They're both strong and healthy already, but I bet it couldn't hurt to try, and they're fairly inexpensive. Which surprised me, I thought they'd cost me an arm and a leg.