Sorry to hear you find yourself on this forum and feeling the way you do.
Personally I didn't tell anybody until I had been given the diagnosis. I didn't want people to worry unnecessarily until I knew what I was dealing with.
Once I was diagnosed I was able to tell them the exact details and what the treatment plan was. For me it was better as I didn't want them to worry (potentially unnecessarily) and when I did tell them I could answer all their questions.
