+1 on talking to your wife and telling her how you feel. You might tell her that in looking out at the future and becoming an empty nester, (and then two retirees at some point) you are afraid. You look out and see that soon you and your wife will have more time for each other and that each of you will become a more important source for each other's happieness as work and children disapear. Tell her that you want to work on your marriage and one aspect of your relationship that you feel really needs to be worked on that would help you bond more closely with her is the sex life the two of you share.
Seriously, read the book SSM, then read lots of different books once you figure out what the "issues" are in your relationship. Then I would suggest getting professional help. Depending on what the issues are either a marriage counselor or a sex therapist. Because of what you have posted, I would suggest starting with a board certified sex therapist. It will be a lot less expensive than a divorce attorney.
What may surprise you is that some of your actions may have contributed to the distance between you and your wife. I know that surprised me, but know I understand that for every action there is a reaction. Sometimes things that my wife did, triggered responses in me that helped build distance between us. We were able to break down those barriers, but it took time and effort. Sometimes innocent things I did were misinterpreted by my wife and built distance. After things get fixed, the light dawns and the reason for the distance become more understandable.
Good luck to you and your wife.
>43 years of marriage--My wife and I are now closer than we have been in decades. I believe that my SSM is over.