Ending a relationship with someone I love

I have been in a relationship with a wonderful person for the last 8 months. At first, when they came into my life it was very unexpected and, after two years of the passing of my fiance, it was unexpected and uplifting and wonderful. It is still wonderful. He is a wonderful and loving and a great friend, but I’ve come to realize that I don’t have romantic feelings and attraction for him and I am spending a lot of time and mental energy thinking about how I should end the relationship. What comes up for me in my thought downloads ultimately is that I am afraid. Afraid of hurting him, afraid of hurting myself, afraid of losing this loving person. I am afraid if I tell him that I don’t have romantic feelings towards him, but still want to be a part of his life, he will end our relationship altogether. I understand this is his choice and that I can make peace somewhat, but imagining the pain he will feel is really hard. Knowing that I am the cause is what is keeping me from figuring out what to do. He doesn’t have any family and I have very little family and I don’t want to abandon him. I want us to have each other.

My model ends up looking like this and I honestly can’t think of any thoughts that would feel right and peaceful to replace my T and F lines. Please help.

C: Relationship ending
T: Ending this relationship will be painful for both of us. It will bring uncertainty to both our lives. It will cause him pain. This will be another loss. It is painful to think of his pain.
F: Sadness. Reservation. Doubt
A: Delay making a decision and acting, feel confused
R: Stay in the relationship and not be fully honest with him or me.