When is it time to "walk away"?

I'm new here and I'm sure it is common for people to start here asking for advice and I will be no exception. Also, hello folks! So this is my first post here. If you care to offer your perspective on my situation I would be appreciative. I have been with my wife for 15 years, married for 5. Things are not so great. After years of feeling as if my wife has "checked out" I confronted her about it and come to find out it's true. She feels no emotional or sexual connection to me any more and states she fantasizes about other men and went on a partying hanging out with single friends bender. As I had already expected this it did not really come as a shock but still hurt. I won't go into every aspect of our situation but as we chatted more she expressed that she felt this way since even before we were married, this I did not see. At this point we are just really good friends with rings on our fingers. We get along great, have fun together and all that. We chat and laugh constantly. This is all fine and well but I need more in a marriage than that, as does she of course. So I really need help deciding what to do. We have talked this to death and are making steps towrds trying to build intimacy in our relationship but I'm not sure I have the heart. She has been pretending to be interested in me in that capacity during our entire marriage and I just can't see past this. I think this cut too deep to get past. Knee jerk reaction, should I stay or should I go? I don't know how to make this decision so any guidance on that might be helpful as well. Thanks in advance if you decide to chime in.

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