EndingsLTA,
I resonate with so much of what you said that I don't even know where to begin.
"I am sad but relieved, confused one minute and clear headed the next."
This is such a hard place to be. For me, it didn't start easing until about four months in. Our situations are different, though. I have a husband, and there was a lot of self-pressure not to ruminate about the affair unless we were actively discussing it. I've since realized that ruminating is part of how I process things, and sometimes I just have to let her go.
"I grapple because unlike other WS/OW situations I read here, I knew him very well before the A and there had never been a need for putting on a mask."
I didn't know my AP since childhood, but I did know him for years before it became an affair. There were never any flirtations or boundary crossings until there were. By that point, it was too late to put on a mask because we'd already seen quite a few downsides (and upsides) to each other—anger, frustration, laziness, sorrow, and all the rest.
"And I am terrified of looking in the compartmentalized box."
That box is a bitch. Excuse my language if cursing isn't your thing, but 🥵.
I've discovered that my story wasn't what I thought it was. So much of it reaches all the way back to childhood. It's been dismantling and humbling, and there has been a lot of grief over here.
There's a famous illustration about grief and jars that has stuck with me. People often think grief gets smaller with time, but the reality is that your jar gets bigger. The grief itself doesn't necessarily shrink; your life expands around it. I think I'm in a season where the jar feels like it has shrunk again, and the proximity to my pain feels overwhelming at times.
I don't know if any of that resonates with you, but if you decide to start looking in the box, you'll have company here.