Once upon a time I was with a woman for 11yrs (for real) and during that time her friends, her younger sister all told her that I was gay, it hurt, but more than that it was a scary thing to hear because I had known it all of my life and even called myself 'bi' before accepting that I am gay. I believe that being with her has given me a greater understanding of myself and of women or woman since they are not all the same and that what you are describing is something similar to what I went thru. In the end we agreed to untangle ourselves financially over the period of a year and then I moved out at that time. It set her free to find a man who is heterosexual, she may have had to worry about other women but that is better than living in limbo wondering if her husband is going to cheat on her with another man. Looking back we were nothing more than party pals who slept together all of the time. I caved to society's idea that I had to date and marry a woman, so I sucked it up and did just that but I have to say that before her there were no men sexually for me and two women, so although I knew that I was gay I ignored how I felt and denied myself the truth. I should not have been married because it was all a lie, yes I loved her, yes I found her attractive and yes we had great sex, but there was always an underlying shadow that got in the way of the both of us. I became depressed from suppressing who I was, she became angry and cheated on me with other men. I outed myself to her and we parted within that one year time frame. I met her 'other' man and now she's married to him with a 19yr old son. Setting the both of us free was the best thing that I could have done for the both of us. Be yourself, set her free, set yourself free and move forward wearing your new shoes, you will be so grateful to yourself and will find that you can breathe easier, and sleep better an night.
I wish you every good thing on your path to sexual freedom and honesty. The love you shared will fade, but if you don't have a nasty background at the end of the marriage then you can look back on fond memories with no remorse that you waited so long that now you're both too old to find a HOT man. Let go while you are young no matter how hard it may be, you will thank yourself in the end for liberating your life and finally being able to step into the life that you should have had all along. If hurting her is holding you back from filing, talk to her about it and then do it for YOU otherwise the sham of a marriage will end up hurting the both of you over a long period of time, and that is more destructive than the finality of a divorce could ever be, the both of you can be free to make plans, move forward and start to feel excited about life again. The truth wins every time. Good Luck!