Betta with Swim Bladder Disease or something worse?

Question
Hello,
First of all I've had my beautiful female betta, Missy for almost a year. She has lived in an established 10 gallon tank for 10 months and with a young pleco for 6 months. When I first got Missy, I unknowingly overfed her for few weeks and she developed what I believe to be Swim Bladder Disease. When her symptoms started she had a slight bend in her spine, swam a little sideways, and couldn't easily turn right but otherwise she was behaving normally. At that point I looked up remedies for it and began to feed her bits of shelled cooked pea every 2 days for 3 weeks. She loved the pea, but nothing changed in her movement or appearance. I raised her heater to 82 F and tested water conditions for changes in Nitrates, Nitrites, and ph every day but there were very little to none. (No sign of any chlorine or ammonia) I also did regular water changes every week. It didn't seem to affect her behavior so I stopped trying to fix it in hopes it would slowly get better.

Now here's my real concern. About 2 weeks ago Missy stopped greeting me and begging for food, instead she stays on the bottom of the tank, only coming up for air in quick spurts. She can't easily control the direction she swims and can't turn right at all, only left. I've also noticed she is breathing heavily, but no sign of ich or velvet. After fasting her for two days I tried to feed her again. Instead of feeding her usual pellets I've started frozen brine shrimp in hopes they wouldn't clog her system more, but I can't get her to come up to feed. I'm now using a turkey baster to feed her brine shrimp on the bottom, and it seems to be working well. She has an appetite but looks exhausted all the time.

I'm very worried about Missy and wish there was something I could do, but it feels like I'm out of options. Any information or advice you have would be greatly appreciated. I love Missy and don't want to see her go!

Answer
Hello,
Missy must be treated quickly.  Overfeeding, and poor diet lead to constipation, then to Swim Bladder, and if left untreated this disease will lead to dropsy.  Dropsy is very difficult to cure if not impossible.  Missy should have one pea a week, and always with the outer shell removed.  Cut the pea into tiny pieces, and feed them to her one piece at a time.  On the day you feed her the pea, she should have nothing else to eat so that she can clean out her system.  Once she is better, vary her diet.  Daphnia, should be part of her diet, as well as betta pellets, betta flakes, plankton flakes, brine shrimp, bloodworms, mealworms, and glassworms.  She should be fed 2-3 times a day in small amounts.  Example:  2 pellets, or 2 flakes for one meal.  Her tummy is the size of her eye, and we must always remember this when feeding her.
For now, do a water change, siphoning from the bottom, add stress coat, and buy "Tetracycline"  Remove the carbon from the filter when medicating.  The water will be yellowish, but this goes away with fresh carbon once the cure is over.  Do not wait.  You must act quickly, or Missy could get worse in a matter of 24 hours, even less.
I hope this helps.
Lynda