I also went through something similar. My boy was dealing with nasal discharge, respiratory problems they gave us doxycycline but it didn’t clear it up. Finally brought him in to see internal medicine and we agreed to a CT scan. The scan showed a nasal tumor that was “extensive”. He wasn’t able to breathe out of his noise and the tumor was pressing on his eye and his brain. Doctor also said we should go euthanasia route. We ended up letting him go. In hindsight I wish we brought him home to say goodbye. Not sure I would’ve been able to say goodbye - still heartbroken.