You are in the place I was about 2 years ago. Not wanting to end my marriage and yet not getting my sex needs met inside of it. So for many years before I reached that point I had been meeting my needs outside of my marriage. My wife's silence on the matter made me feel OK about doing it... But it wasn't OK it was hurting her and I was hurting myself (hurting my daughter too).
Finally I got tired of being stuck at Schnarch's level 1 and 2 (don't fool yourself that's where you are too). I wanted more and I wanted a mature love and sex life. "OMG I hate the life I am living - it's a lie. I am lying to myself and to my wife. I know I am capable of leading a much more fulfilling life than this sham."
I wanted more out of my marriage. Those higher levels are the reasons I got married. I wanted to know my wife in the deepest possible way, I CHOSE her because I wanted to experience:
5) "Partners realize and appreciate each other's deepest core personality and potentials--pushing themselves to disclose their most private and personal truths."
6) profound bond with a single partner in which "sex becomes a form of spiritual communion celebrating the mysteries of life"
My wife is like yours in that she feels very inadequate about her sexuality. I made that even worse by attempting to meet my needs without her. It was the worst possible thing I could have done to her.
I not telling you what to do here. I'm just saying that I reached a point where the way I was living no longer felt right to me. I wanted to grow and it was me that was holding myself back. The last thing I wanted was to end my marriage. When I came to a point though where I could let go of the marriage, let go of my wife - she found that she wanted to grow along side of me once more. It was my letting go that brought us back together.
I hope you will find your truth too ssmguy. You are here, it seems, to do that.
