I completely understand your feelings. I myself have had trouble telling others simply because it makes me vunerable to attack. I am guarded with some of my secrets and the things that have happened to me out of fear that the person learning it, will then use the information against me.There are insecurities around trust that come into play, issues with denial and the sharing of information making it 'too real' for me to cope with, as well the shame issues you mentioned.
I did finally open up to one person, out of need, and told them my biggest trigger. This person, if they so chose, could pretty much distroy me with this information, but I needed to share it with them.
So I understand much of you fear and tripiditation at sharing your past. I also know that fear sometimes acts as chains keeping us bound to the past, and preventing us to find freedom from the past, and keeps us from embracing a better future for ourselves.
Ok I will stop preaching now. I just want to see you get better.