Florence.....a couple of things that I take note of, from your post.....
You were high school sweethearts with 20yr. history....so, you must have been mid teens when the relationship started.....
Young love--first love--tends to have an intensity that is marked forever in our memory...Not necessarily, because it was the BEST love, but, because it was the FIRST love...
I think of all the people who say that they still remember their "first love" with special feelings....
You were with your Ex for 20yrs! Just by lovgevity and the time he came into your intimate live...he is a part of the fabric...the memory of your life.
Just because he was there!
Comparatively, your new person is much newer on the scene....so, you can't possibly have the amount of history with him, as your ex.
History takes time to build.
Of course, I don't know if this newer person is enough for you, on all levels..
He may or may not be...how could I possibly know...lol....?
But, I do think that you should not be unduly alarmed by your feelings about the ex.
I think you will grow past their "importance" with time.
I know that I did!
Another thought....With my children's father...after the divorce..I seldom even laid eyes on him. He was a jerk, so that I kept contact with him to as little as humanly possible, given that there were 3 children.
I watched from a distance while they got into the car with him. I waited in his driveway, if I was picking them up....
I let my kids talk to him on the phone, when he said he was picking them upo for a weekend. I only spoke on the phone if absolutely necessary.
(almost like self-imposed restraining order "rules"...lol)....
I think that the less contact you have with your ex...the better, for you....