well, i don't know...

If it wasn't obvious by the username, I struggle with this as well.
Have you created a reboot plan with him? This is what I'm working on with mine this week.
We're going to start doing weekly check-ins about his recovery and also my own triggers, and relationship recovery.

Definitely sounds like you struggle with Betrayal Trauma like so many of us SO's.
You should write down your triggers, at least. Things that trigger your trauma, flashbacks, anxious thoughts, etc.
Just so you have it to look at, and see how you're doing with them as time goes by. Mark your triggers on a calendar.
He could do the same as part of his recovery.
"What if" is so damaging. I know it's so hard, but it needs to disappear from your thoughts if at all possible.
Try replacing that thought with "if _______, then ________ will be the consequence." Black & White.
There are grey areas, which may be difficult to identify. @Kenzi has a great thread on this. It's linked here.
If he's serious about his recovery, he will understand that you need to do this.

Also, take care of you. Keep doing the things that make you feel good. I know, going into "fix it" mode can feel like the safest thing to do.
But take care of yourself. You're not alone.