It may just be that he is shedding. I know that my female panther is wierd sometimes around a shed.
Also, look at what kind of food he eats. It may be that he is just sick of a certain few, and that he needs to try something new. This is one of the trickiest things about chams! The lil buggers are so darn fussy! lol. Try to get him to eat by offering a new kind of insect, if possible.
If, after a week or two, he is still not eating, and his behaviour seems off, it may not be just a hunger strike: he may be sick. If he doesn't start eating on his own you may want to go to a qualified vet who can give him a look and see if something is taking away his appetite.
Best of luck!
~Lindsay