[Francois]

Here is what I have to say, having had a similar problem to you. Get to a psychologist, and have the psychologist help you. You can get an official diagnosis, and maybe even a direct recommendation from the psychologist for the school to give you an extention. If not, present the diagnosis and ask for an extension. Getting extra time for your assignments is a rather easy thing administratively, which would be the main thing they would worry about. You won't however be able to postpone examinations easily, due to the massive administration involved. You may however be able to extend the time limit on a paper.

Without a diagnosis from a professional such as a psychologist or a psychiatrist, you are unlikely to get any extra time though, unless you have very understanding teachers...