:( I have a 5 week old chiuahua puppy and he doesn't seem to be eating right, what should I do?

At 5 weeks is pretty young yet. Is he completely weaned? What are you trying to feed him?

I discussed not eating in detail at https://www.askmehelpdesk.com/dogs/information-articles-our-dogs-expert-labman-53153.html#post254171

If you have only had him a day or 2, continue to offer a decent dry puppy chow and plenty of TLC. Also a 5 week old Chihuahua needs very little to eat.

Nearly everybody agrees 5 weeks is too early for a puppy to leave its mother and littermates. Still I think you will have fewer problems than after 12 weeks.