My cat is 8 months old ,,,he has up until now been in perfect health,typical of a young neutered male ,,very friendly,active and curious. two days ago he became very lethargic and is dry heaving,sneezing and coughing up a small amount of clear saliva, also eating very little. Im not sure if he ate something he wasn't supposed to or if he has an upper respitory infection or the flu,,,,please help!!