Saphire - I would get the test if I could afford it right now. I still owe the vet $2,500 and can't just drop the money without a LOT of consideration.
The picture isn't the best (hoping I did it right) trying to get a picture of him standing is like trying to nail jello to a tree. He's only lost weight after he had to be on the special diet after surgery, other than that he's looked thinner from growing but gained weight. He's lanky, very thin at the back end but his ribs aren't showing unless he turns. You can feel them but he doesn't look emaciated.
He's been eating everything in sight since we brought him home at 9 weeks old, he's actually getting better with leaving some things alone with age. But he's never irritable, never reactive and always a happy pup. No loose stool, on occasion he'll get an upset tummy from getting into something but he is almost always back to normal within a day or two.
He got neutered 2 days ago, he's been training to do SAR (lots of pretty female GSDs that I'm forever having to keep him away from) and I needed to do it when I had some time off to recoup him. I didn't know it could make things worse, our vet said it was about time and he's been through 2 surgeries before so I figured he'd do fine just like with them.
His dog food isn't high fat to my knowledge, I'll look into it and the probiotic/digestive enzymes.