In my experience, telling someone about your diagnosis is tricky. Sometimes it can be good and sometimes it can be bad, and I don't seem to be able to accurately predict someone's reaction to that information. People who I thought would react badly have not, and people who I thought would react well reacted badly.
So here is how I make my decisions about telling someone my diagnosis, and it might help you.
First, I look at how important this news is to the other person. For example, I felt it was important to tell my boss but not my coworkers because it is important for my boss to know in case I ever need assistance of any kind at work, but it is not important for my coworkers to know.
Secondly, I look at how I would feel if this person reacted badly to the news, like if they said they thought I was just being whiny or stupid by thinking I'm autistic. For example, I haven't told a couple of my sisters because it would be hurtful to me if they reacted badly.
I take those two factors together to make my decision:
If it IS important and a bad reaction WOULD NOT bother me, I tell them.
If it IS NOT important and a bad reaction WOULD bother me, I don't tell them.
If it IS important and a bad reaction WOULD bother me, I consider which factor is stronger.
If it IS NOT important and a bad reaction WOULD NOT bother me, I consider which factor is stronger.
For example, I told my mother and one sister because, even though it would be hurtful to me if they reacted badly, it was MORE important to me that they know about it. I do not tell most of my acquaintances because even though it would NOT be hurtful to me if they reacted badly, it is also not at all important for them to know. My close friends know, some of my closest family members know, my boss knows. Most everyone else does not know. I SHOULD tell my medical doctor because it is important for him to know (since medical research is increasingly showing a physical component to autism, such as gastrointestinal issues), but I haven't yet because I think a bad reaction from him would be hurtful to me.
I hope that is clear and that it helps you to decide what to do.
Also, one tip that I have found to be somewhat helpful when someone tries to say that I'm not autistic is to tell them that I was diagnosed by a professional therapist with special training in autism (which is true) and that it is not simply my own diagnosis.
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You don't need to hide, my friend, for I am just like you.