Would you TELL NGF that there was something missing, you can't tell what, but you are willing to stay with her, anyway? That you will never open up as fully as you did with your xw? How do you think that would make her feel? Has she always been more into you than you are into her, or is this a fluctuating (normal up & down) thing? It just seems like you are settling so you are not alone, maybe even until something better comes along...? If you can't have that kind of intimate sharing, what are you doing?
Again, I could be totally off-base - if that's the case, please ignore me!