I hope you're able to find out what's going on so you can start on a treatment path so Milo feels better.
Has he gone off the Rawbble too? We are so conditioned to feed our dogs kibble, and it is so easy and affordable, it's hard to move away from it. But what's most important is that he's eating. Wiki is still loving the Stella & Chewy's raw patties. And she thinks that cheap, gross canned food are the best thing ever (Pedigree and Puppy Chow). For the last 18 months or so of her life Lila just ate chicken breast and egg noodles and did just fine on it.
Hang in there!