Hi Something Happened My Cat Recently. I Don't Know What

Hi something happened my cat recently. I don't know what but he could bearly walk straight. He looked drunk & scared. He had lumps of fur pulled out from his neck but no blood or marks. He was very quiet so I took him to the vet . He had an abscess on his neck which burst. It took him 3 days to get his balance back but now is he peeing everywhere which is out of character & his behavior still isn't the same. He is very quiet & hasn't meowed since that night when something obviously happened. The vet couldn't figure out what was wrong. Please help