He must be getting some food - unless someone is spoiling him with treats, no dog that small could eat nothing for weeks and survive. As she suggested, pick a food and stick with it, and elminate "between meal snacks" as well, until he gets back on a regular schedule of eating. It'll be tempting to sneak him tidbits here and there, but that he eats his own food is more important. Nerves of steel - that's what it may take. I know those big brown eyes will try to melt your heart ... but if he's been vetted recently and is otherwise healthy, you know what to do!