An update on our foster boy Ty

Ty is not doing well this morning and Andrew is taking him up to the vet at 11am. He was doing great last night, from 7-8pm I had him out in the yard with 6 other dogs and he was running around and having fun. I brought the kids out and with Connor running in the mix I put him away and he cried at the gate to come back in and join the party. This morning I got up to go and get him from his kennel and he is listless. He has had diarrhea since he arrived. It's gotten better but it's still very mushy. I'm still adding pumpkin and yogurt to his food but he's back on kibble. About a week after he arrived he started drinking excessively and urinating constantly. He wasn't making it through the night. I didn't think much of it though since excessive drinking/urinating is a sign of thyroid issues and since we have been messing with his meds I wasn't really concerned. He was happy, his tail was wagging, he loved to come out for his walks and loved to work for me in the cul de sac. He was so proud when he figured out his heal and come. He just pranced on his leash when I'd take him out. This morning though he won't even lift his head, he follows me with his eyes. I lifted his big head back on to his bed as he was laying with it hanging off. I sat with him for awhile and told him he's a good boy and have had to leave him because my babysitting kids are here. I covered him with a blanket and turned the heat way up on the kennel as he feels cold to the touch. He's heading up to the vet at 11am (Andrew's coming home from a meeting to take him). If he gets here sooner he will take him sooner. I now think it's something worse and wish I'd done something sooner. I'm really worried that this big boy may not be coming home :-(