I'm going to keep a story from my past a secret from my friends
Is there a reason you'd keep it a secret from your friends?
I feel my friends would be very judgmental towards me about it.
You should usually confide in your friends, as they would in you, without withholding information.  However, if you are ashamed of something in the past, and if it doesn't affect your friends today, it's okay to put the past away.
Go talk to your friends about how you hate yourself whenever you get nervous.
If you don't feel comfortable with sharing information with your friends, then something is wrong in the friendship. You should think of it as friends should always be there for you, and talking with them about this may be beneficial for you.