I don't know your situation at all, so forgive me if this has been covered, but are you taking steroids after your surgery? My mom had surgery on her brain and had to be on steroids for quite awhile to keep the swelling down so she could heal and let me tell you.....She is usually the sweetest thing and she was a GROUCH. She would gripe at somebody and then look at them like she couldn't believe what she just said.
Either way, I'm sorry you're having such a struggle. Don't get too frustrated with the changes, just give yourself time.