Hi
My dd has a dx of AS. I think that I expected to feel relief at her dx, as it would open doors top get her the help she needed etc. And there was an element of relief that we finally had the 'answer' if you like.
However, I have to say that I still felt shocked and shaken, even though I was expecting it.
There was an element of my fears being confirmed and of sadness, for some reason. I think that it is only natural do go through a range of emotions - grief, sadness, relief, guilt, anticipation. Then I reached a stage of acceptance and the dx, to me, just became a name for all of the 'quirks' dd always had.
I don't think there's a lot you can do to prepare yourself, as the emotions don't really hit you until you get the dx.
The best advice I can give you is to see it as a positive thing -it will allow you to access the help your ds needs. And be kind to yourself; give yourself time to absorb it all.
Also, try to keep in mind that first and foremost, he is still your little boy and a label attached to a dx doesn't take that away. He may have some additional needs and 'eccentricities' but that's what makes him unique. And life will never be dull!
Good luck x