Betta with lengthly illness

Question
We purchased a betta a few months ago at a nature center charity auction.  We put him in the tank and used the water treatment and food products he came with and he was doing very well.  Then about five weeks ago he stopped being active or eating, dulled to almost a grey color, and the inside of his gills became very red.   
I moved him to a slightly larger tank (1 gallon) with a filter and light, treated him with Melafix, and added freeze dried blood worms to his diet. His color has returned to normal and the redness inside his gills has cleared up.  He is eating a little better, but is still crashed at the bottom of the tank most of the time.  When he does go to the top and swim a bit, he is very jerky - almost like it hurts him to run up against anything.  I do partial changes of his water every two days or so and a full change once a week. (I keep a reserve of treated water next to his tank).  I fish out any left over blood worms with a net.  Is he likely to ever recover fully? Is there something more I should be doing for him?  

Answer
Hi Mary,
He sounds like he has swim bladder disease. I recommend not to change the full tank as much as possible because the completley new water makes your fish more prone to disease and also shocks the fishes system. Hope this helps,
                                            Samantha.