I guess what I was really looking for when I posted this question, was some advice on how to reach out again, and whether or not it's a good idea to be honest with my friend J about the anxiety that I feel when we correspond.
"Feel the fear and do it anyway". A cliché, yes. But there is truth to it even so. If the anxiety is not crippling, then maybe just taking the action, in spite of how you feel, might be your best bet.
Also, you will scare J off if you share too much... are you sure? Are you absolutely positive that J will be scared off if you are open and honest with her? Isn't it just as possible that J might be as accepting of you as she was before? Isn't it even possible that she might appreciate that you trusted her with what you are struggling with right now?
I don't know the answer to those questions. I presented them as a means of inviting you to gently challenge your own thinking on this, to introduce a little flexibility into what you believe. As Toby points out, cognitive therapy can prove very helpful in situations like yours. You can begin to practice a little cognitive therapy on your own, right here and now by consciously working with the thoughts that leave you feeling anxious.
Good luck NC and god bless! Remember, J may have been an amazing friend to you, but you would also have to be amazing to have that kind of friend in the first place! :-)