Something I saw on animal cops about a dog who had distemper , she had squinty eyes , and when you touched the top of her of her head right in the middle, the dog would automatically flinch. It was a neurological response. this dog was very ill. Unfortunately she did not make it.
I am very sorry your baby is so sick.
My thoughts and prayers are with you and your little puppy. The hardeset part is not knowing what it is that is causing the sickness .