Hi Bulcy,
It's good to see you hanging in here and persisting in processing.
Did you ever read the Harry Potter books? Kind of a lame metaphor that struck me with your situation, but it's one that stuck recently. My kids and I read books together at bedtime. I love books and we often have really good discussions around what's going on in them. The kids are awesome- I love hearing their insights. And on bad days when we're all tired, it's a nice relaxing escape for us.
That said, DS and I reread the last book of the series, Deathly Hallows recently. In there it talks about Voldemort splitting pieces of his soul off and attaching them to inanimate objects by committing a horrible act. In his case, it was murder. He did it in an attempt to make himself invulnerable to death thus invulnerable to pain and destruction he caused.
Are you starting to see the parallel? The horrible act of infidelity genuinely damages our souls (so I believe). We end up having to split off parts of ourselves (compartmentalize) in order to keep ourselves invulnerable to the pain of the destruction we're causing. Not just pain to ourselves, but pain to others. Our souls are damaged in the name of invulnerability and avoiding pain.
In the book, it talks about how those who split their souls this way rarely reunite themselves with the pieces of their soul they split off. The pain is so great, it nearly kills them. The fear of that pain keeps them from reconciling with that piece of themselves.
So yeah, long way around to saying that you split your soul into pieces every time you were unfaithful to your wife. Each time, a part of you was left behind in order to protect yourself from the pain of your actions. Since you've had such a long history of waywardness, it's going to take you a long and painful time to reunite and reintegrate yourself. The memories are going to be hard to recover because you've blocked them out for so long. The memories are the pieces of your soul that have to be reunited to yourself in order to be whole again.
In the book, Voldemort could not love. He was too broken and too concerned with his own greatness and immortality. He needed that greatness to protect himself from the rejection of his parents and the pain of growing up in an orphanage as a poor and neglected child. In some ways, we're all like that on the wayward side. Too broken and scared to trust and be vulnerable. Too scared to open ourselves up and really love wholeheartedly. We use the A's as a means to become invulnerable to the pain of feeling our own inner dialogue of our insignificance and failures as people. We split parts of ourselves off with each wayward act as a way to make ourselves invulnerable to the pain and destruction we're creating.
The pain of reuniting with yourself is going to be a long and scary process Bulcy. You've closed yourself off from the worst of yourself for so long, that there's likely pieces of you you've forgotten existed. Your mind is so used to walling yourself off from the shame of your acts that it's going to be hard to pry the memories out of your head. It's necessary work though.
As for forgetting some of the details, well, I like what my confessors (Catholic) have told me: "If you give me every gory detail, we'll be here all day. Please give me the meat of the sin. God knows the details, He can handle the rest." Go with that- the meat of the events. Details... are details. 20yrs is a long time to remember the small stuff. Give your W a fair accounting of things like, "In October of '01, I slept with this person at a hotel in this city." Surely you can dig that out.
In the end, your BW will have to be satisfied with your answers. But first you need to be satisfied with yourself for digging them out. I believe you are sincere in wanting to come fully clean, that's why I'm saying you have to be satisfied first. When I first came here, I was looking for any excuse to justify what I'd done and would have loved to get myself off the hook with a, "but it was so long ago I can't remember" excuse. I don't think that's where you're at. So, keep digging, and don't sweat the small stuff- find the meat and give that to your BW and yourself. Only then can you really be whole.