I have a veiled chameleon named Hulk who is 5 months old. He has always hissed when you try to put your hand over top of him but would always come to me if it was underneath him. Lately, he won't let me get near him and if i try to he will just try to attack my hand. I open his cage everyday to feed him and he puffs up when i do. I'm not sure what to do about this. Any help?