Is Milo's playing, eating, drinking, etc.. normally? If so, I don't think there's anything to worry about. If anything, I'd say he's growing up to be a Teapot!
From what I've been reading, unless you see something unusual about him (lethargy, vomiting, etc), there's no such thing as a fat puppy. And just from what I see in the picture, he doesn't look fat to me at all. But that's just my opinion. I'm sure others will be happy to chime in~
Keep in mind that Yorkies come in variety of sizes, shape, colors. But if you're worried, it never hurts to get a vet to check him out.
