Hi all. long time lurker who is battling with some difficult feelings at the moment.
Have been with DP for 10 year and have on the whole had a very happy relationship. I moved countries to be with him and have since settled and built a life here for myself (as well as with him) with a job and prospects. My DP is a wonderful man. On paper, he is charming, considerate, supportive, funny, and we generally have the same outlook on life. We are great friends.
Here comes the BUT. I just no longer have any romantic feelings towards my DP - like many other posts I've come across, I feel like I'm living with a housemate or a good friend. This has been brewing for 2-3 years and I kept trying to change my feelings towards the relationship, but I just don't feel anything. I no longer see a future with him. I have begun to think about moving back to the UK, but when I imagine it, he is not in the picture. In most of my thoughts about the future, he does not feature.
Our sex life has always been relatively OK - nothing special, but I certainly do not enjoy it anymore and it feels like a chore (and we only do it once a month if that).
I've tried to talk to him about it and my feelings, but he clams up and blames other areas in my life that he thinks are causing me stress. I cannot seem to get through to him. He knows I am not happy and told me the other day he had had a nightmare where I had decided to leave him :(
I have barely been single in my adult life and am very nervous about what might come next, but I do not see myself spending the next 40-50 years with my DP. We don't have any children, and are relatively independent financially (so logistically it would not be a complicated split - except shared belonging etc.) but of course we have a lot of shared friends and my family absolutely love him & he sees them as a big part of his life - I think that is going to be very hard. 
I guess I'm posting here to tell you my story - I am actually considering ending the relationship and I know it will destroy him. To see him hurting will be devastating, but I am trying to find the courage to go through with it. I feel treacherous but I know I have to do this to get some happiness back in my life. Or hide under the duvet and spend the next 40-50 years being a chicken