I know I'm a bit late on this one, but our old boy had all the same symptoms... for YEARS. They kept telling us he was perfectly healthy, nothing physically wrong with him. He had a really bad bout of diarrhea with a lot of blood a couple of years ago, so we rushed him to a vet in the new town we had moved to and they diagnosed him with Colitis! They said he likely had it since he was a puppy, and it's not easy to diagnose. In fact, none of the blood tests that we had done over the years indicated anything at all.
We now have to feed him smaller amounts more times a day and make sure he has something in his tummy before bed. He also gets yogurt daily along with a probiotic. He hasn't had a bout of colitis in awhile now. He still has them occasionally, but nothing like they were before. Good luck and I hope you can figure out the issue!
Oh, one more thing... Thorin can't take Salmon oil at all. It gives him loose, mucousy poops. He has cancer, and just finished his chemo. Salmon oil is very beneficial to cancer dogs, but again, his tummy can't take it. I do feed him a cup of fresh cooked wild Salmon daily and he seems to be fine with that.
"Obey my dog!" - Mugatu
"Who can believe that there is no soul behind those luminous eyes!" ~ Theophile Gautier
"Dogs are not our whole life, but they make our lives whole" - Ok... whoever said this has never had a sick or special needs baby. They ARE our whole life!
R.I.P. my sweet, handsome Thorin. You are missed dearly Dec. 25, 1999 - Mar. 4, 2012