Seeking expert testimony is a sign of strength. A personal relationship with a caring professional is proven clinically effective.
If I understand correctly, you have not had much of a relationship for over 15 years, when your committed relationship turned into something else - a strong friendship/roomate status.
You have tried and tried. You are getting close to the point of giving up - meaning to abandon hope of a husband wife relationship and then either: live together as friends and roomates while you remain unfulfilled and unloved for the rest of your days, or; separate and divorce and start a new chapter in your life.
It may be difficult to accomplish, but it is the best hope for you.
I noticed that you have not visited a sex therapist. A sex therapist is a mental health professional with additional training and national certification. He or she are experts at solving problems such as yours.
The way to find a certified sex therapist is through the AASECT site:AASECT - Member Directory
Click on your state and a list will appear. Choose the therapist that best suits you.
If you cannot find one nearby, then go to:
www.psychologytoday.com and click on your state and city and search in that site under marriage therapy or sex therapy.
If this doesn't work then you must decide on how you wish to spend your future.
I shall keep you both in my prayers.
Elliott, MAE, LPCC, NCC, CCMHC