I hear you. It's a tough one. I sometimes feel that way as well and I know how much it can hold you back.
The way I figure it is that I have completely divorced my old relationship and now am trying to reconstruct a new one. So the insecurities are exactly the same as if you had no past, like you feel at the start of a new relationship. This mostly works for me.
Another way to think about the insecurity is to think back on all you went through to get your W back. That has got to mean something in her mind even if she does not express it right now.
