Something is wrong with my cat?

My ten year old cat got out of the house and ran away it was about a week and a half before i found him. he seems to be happy to be home but about two days after i brought him back i noticed he started hacking. At first i thought it was just a hairball but now he is coughing up a spit like fluid and sometimes it is foamy. His meow sounds weird too and now today he will not eat anything and he barley drinks any water