where is the cage located.. is it in front of a window or a door.. do you have any other pets such as a cat or a dog that could bother him.. do you have him in a tank.. he is probably not mean just scared..if you have him in a tank he could think you are a predator since your hand comes down from above to pick him up. has his diet or cage changed recently. all of these things could be a factor. i can't remember but were you able to hold him before??? or hasn't he been held much. i know last year when i went away to school i left spike at home with my mum and she never picked him up.. just fed him cleaned his cage and talked to him oh and petted him but never picked him up .. the only play time he had was on the weekends when i came home and after i came home this summer he went from a grumpy gus to a happy lil boy.. getting out twice a day and "rocked" to sleep at night.. so just be patient...he should turn around..
btw my beardies are the reason i'm living at home this year 
alissa
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2.2 chinese water dragons
1.2 bearded dragons
0.2.1 leopard geckos
1 african clawed frog, 1 african dwarf frog, 1 california newt
1.4 english setters
2.2 breeder mice
tons of fish