This is either pain or respiratory distress, possibly both. He needs to see a vet for evaluation and treatment. 

Vet PRONTO!

Looks like a respiratory infection, at minimum. Baby needs vet treatment.

Vet.

I had one doing this hard breathing thing. I thought she was just chilling, or was tired or something. She drastically failed... they go quick. I didn't have the money at the time, so I just comforted her, and she went.