Why does my 5 month old yorkie burp all the time?

Because Iams is terrible dog food. His burping should prove that to you. Do a little research and comparison shopping and I'm sure you can find a good, high quality dog food for him such as Canidae, Wellness, Innova, Evo, Halo, Merrick, Blue Buffalo, Taste of the Wild, etc. There are more.

As a general rule of thumb, if it's sold in a grocery store - it's garbage. Shop at feed stores or pet stores such as Petsmart and Petco. But, get rid of the Iams, get a good quality dog food and I'll be his burping stops - other than the occasional burp right after eating, which is acceptable.

lol ask the vet. btw i marked this q as interesting. i think my doggie only burped one time, the only time i caught him.

Iams is a crap food, maybe he can't digest it.