Hey, I have a lot of anxieties like this too.
It sounds like you told him on a sort of "whim," insofar as you weren't really ready to tell him. You may have thought about it beforehand but you didn't wait long enough to make sure it was really something you wanted to do so the action of telling him and the change it wrought in the way you felt about and thought about telling him happened too quickly for you to process it and come to grips with it. Are you having an uptick in general anxiety and stimming in general? If so, I'd say that is a sign that you are reacting to the suddenness of the change in the way he might perceive and the change in being known for what you are and being seen more clearly. You aren't used to "being known" as a person with AS. Even though he probably knows very little about it, you know a huge amount about it and so you feel like you've just told him everything about your innermost soul, but remember he probably doesn't know as much as you do and it doesn't feel as unsettling to him either. I'd be then wondering the ramifications of having told something so personal. This may not apply to you in any way so feel free to say so; I am likely to be projecting.
Or are you now only wondering about the ramifications of having told him? Like who he might tell, what he might think about you as a result, and/or how he might act towards you, if it will change his behavior towards you or change your behavior towards him or with him just because you know he knows and you might be feeling really awkward or uncomfortable with that?
Sorry to psychoanalyze. It's how I roll.
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RDOS Aspie Score: 145 or 144/200 Aspie, 68 or 57/200 NT
Defies categorization. A mixed bag.