how many times have you moved him around? Some Discus take longer than others to get used to their new surrounds - if you have moved him around alot it may not have given him enough time to get used to his new home.
If it was my fish - i would try taking him out of the discus tank and putting him in with smaller - less aggressive / territorial fish - feed him up a bit and once he has some energy up and meat on his bones - try to re-introduce him again - having said this - as you may know discus are school fish - this MAY do more harm then good.
What foods have you tried to tempt him with?
Also - you may benefit to ask the place where you got him - what the pH levels were - if they were in the low 6's- and you put him in the high 7's - could be shock?
He MAY have worms as previously mentioned - check around his gills for fluke - or check his poop for internal worms - if you don't know what to look for - google it - sometimes images are easier then to explain.
Lastly you could risk it and try feeding live foods and he may eventually take - depending on how he was when you got him - discus can go several weeks without food - eventually they will bite the bullet and feed - maybe see what the seller was feeding him before you got him and grab some of that for the time being.
thats all i got - sorry if its no help