sick mouse not eating or drinking

Question
Hi,
My Male mouse who is about 9 months old has been very sick for the last week. He started chattering while i was away last week and when i returned on friday he had stopped chattering but is sleeping constantly, is very slow, weight loss, hunched over with messy fur and is refusing to eat or drink. i have been trying to force feed him water and vegetable and nut purees but he is not interested in food and spits it out.
i took him to the vet yesterday thinking it was a respiratory infection, they said his breathing and heart were fine and gave me some pain relief medicine for him. they checked his poo under a microscope and couldn't find anything wrong with him. the only thing they could come up with was that he may have an unknown injury.

any help at all would be greatly appreciated
thank you so much

Answer
Dear Emma,

How is he? He must be kept very very warm.

He should be given antibiotics whether he has clear lungs or not. He could have another kind of infection. I recommend doxycycline  and amoxicillin.

Has his behavior changed with the pain medication?  

Please let me know so I can try to help you further,

Squeaks,

Natasha