Take him to a vet

There is this magical place called a Veterinarians office. I believe they take care of sick animals.

Check it out, Einstein.

Take him to the vet.

You should take him to the vet to see if he is alright. He may have something wrong. And even if he doesn't, it's best to get him looked at, they may be able to help. Just keep your chin up, there's always a chance things can get better. It seems like you really care about him, just show him affection, pet him, and everything, and just try to get him into a visit with the vet to see if everything is alright

Depending on the breed and age of your dog, it may be time to put him down. That's what happened to my dogs. i put down a cockapoo in 03 and a yellow lab in 07. They were both over 15 years old, and that's how they both acted for about 3 months before. They lost weight, and gradually ate less and less. They are buried together on the shores of Lake Superior, where they loved to run on the beach and swim in the water. I cried my eyes out for both of them, and I'm a gramma.

Go to the vet now. Emergency vets are a wonderful thing.