I agree with Christina -- try to focus on the fact you're getting accommodations now that you have the letter.

I'm sure it's annoying/irritating that you have "conduct disorder" written in your pdoc's letter, but you can't change the fact your school has already read the letter. You can try to get the diagnosis "fixed" for the future, but between now and your pdoc appt, try your best to let it go so that you don't stress too much over it or get too frustrated. You want to do well in school and you don't need the added stress.