? for parents from adult as pie: how to tell?

hi there, i'm new to the forum. I have a question for parents of kids on the spectrum but i am not a parent, I am an adult, getting assessed for Asperger's this month. I would like your opinions on this--if your child was not diagnosed until adulthood, and was the one to tell you, how would you want to be told? I really want to tell my Mom about this in a respectful, loving way. I want her to know I don't think she caused this or is in absolutely NO way to blame, it's just genetics, just chance, no different than if i had cerebral palsy or diabetes. I want to share this with her but I'm super scared. I want her to know the real me, and why i was such a messed up, difficult child, screaming and throwing things and i didn't know why. I would like her to be with me on this new journey, trying to figure out how to be a better person. I don't always know how she's going to react to things I say, and I don't know if I am saying it wrong, and don't want to mess this up. I'm also scared she won't want to believe that i've got something different about me.  Any advice??? what do i say to her? thanks!!!