For me if there is not intimacy (which disappeared when the trust and respect left) there is not sex. I know some people who can separate the two and sex is just the physical act. But also for me there is almost a visceral no thanks when he asks for sex--along the lines of WTF--are you that unaware.
I remember about a month ago saying these exact words to AH when I told him we needed to divorce or get a legal separation and that he needed to think about them before we had a serious discussion.
I told him that there were currently 3 things that were totally non-negotiable and were not going to change because of all that had happened:
1. I was never going to think it was OK for him to be an alcoholic and drug abuser. Those were things he could only do if he is not married to me.
2. I was never going to think it was OK for him to "be an artist--because that is who he is". He needed to financially participate in the family and that meant getting a job and doing his art at the same time. Being an artist is also something he can do without me. Note: leaving his art would also mean leaving the people he drinks and gets high with too.
3. He was never going to have sex again for the rest of his life unless he cheated on me because I was not interested because of everything that had happened-- that part of our marriage is dead. I had tried to revive it but discovered it is gone.
None of this was punitive on my part--it was just true. I am not interested in a physical relationship with a man who will not get a job to help support his family and has decided that alcohol and drugs are more important than me and his kids. I need the trust and respect and it is gone.
I don't think you are being selfish in any way.