Help!? I don't know what's wrong with my dog!!?

My dog is 4 yrs old. But I have no clue whats wrong with him. He wont eat. He won't drink. Unless ou force him!! He's been like this for a couple weeks now. And well we took him to the vets. And the guy said he's a mean dog. But he had (i guess) what's called a worm inside him. And the vet gave us medicine where we gave it to my dog. And he got somewhat better, but like I don't know why to do. Plus I was gone for a day at my friends and when I came home I was like " heyy Jackie" ( btw his name is jack) and he frikin growled at me. An all I did was pet him. And he growls alot at people. And a couple years ago he attacked my friend. For no reason. But, I don't know what to do! Because like I said he will not eat anything!!! And we gave him 10 different types of dog food. So it's not that, and we gave him canned food. And he still didn't eat that! He won't even eat cheese! Or drink water!! I just don't know what to do. Can you please help me!! Thank you sooo much! And don't just be like " oh just uthinise him!" uhh no, I actually love my dog! He's my bestfriend!! Just pleasee help! Thank you thank you thankyou!!!! ( btw sorry for so much punctuation)