Aspects of this sound more like mania to me (like the racing thoughts).

I have ADHD and it doesn't matter how interesting the work is, I still can't focus on it. Also, I have just as much trouble with 'fun' things like watching a movie, reading a book or magazine for fun, watching tv, etc.

I think it's pretty normal to have trouble focussing on your work if you don't find it interesting. IMO, what makes it 'adhd' is when you have trouble focussing even when you do find something to be fun and interesting (like reading a magazine article for pleasure, going shopping, or watching a movie). That's when you know you have a neurological deficit.