How old is he and what type of cham do you have? Not eating for a couple of days may not be terribly bad for some chams. Mine went for about a week not eating. I noticed he kept trying to get closer to the lights so I added a higher vine (just a couple of inches) and he started eating normally again in about a day or so. Maybe your's needs to get more heat too? Has something changed in the chams environment or has the house gotten cooler recently?