How about me being diagnosed with schizophrenia? I'm really scared but no one know.
That must have been a difficult diagnosis for you to receive. Could you share a bit more with me about not wanting others to know?
I am afraid that others will judge me and think badly of me
Your fear is understandable, but I think that you should allow those who love you to be there to support you. What your dealing with can be managed with medication and therapy, but you shouldn't have to go through this alone. Telling others will be scary, but it will probably feel much better once you do.
But then people will be scared of me. And I don't want to them to think I'm crazy.
You don't know if that's how they'll react and I only think it's fair that you give them a chance. If they love you the they will be open and willing to educate themselves on what you're dealing with. Let them help you, as you deserve the care of others.