Feeling Stuck: How to Deal with Triggers

My husband came home a few weeks ago from work and, like most days, gives me an overview of his day. A funny story, perhaps. A meeting that went well or not so well. This particular day he mentioned that he'd had lunch with a salesperson, noting that he'd offered up, what he thought, was a smart way this person's company could improve their business.
In the telling of this story, something was, to me, notable. He mentioned he'd had lunch with A salesperson. Singular. But as the story went on, he didn't refer to this salesperson as a "him" or a "her" but as "they".
Red flag!!!!
My body tensed. My heart beat faster. My mind raced.
I knew, without asking, that this was because this salesperson with whom he'd had lunch was a she. And I feared that there was something about this she that made my husband avoid any discussion of it.
So I asked him whether this "they" was a male or female. He told me what I already knew.
And then I screeched something about how I couldn't believe he'd lied to me and was this ever going to end and on and on (I hardly remember) about how I can't trust him.
He panicked and doubled down in attempts to placate me. That he hadn't "lied" (Bullshit, I said!), didn't want me to draw the wrong conclusion, that there was nothing. (Heard that before, I said.)
In short, we both blew it.
Our counsellor offered us a far better approach.
She said my response was normal and made it clear to my husband that when he seems to be hiding ANYTHING, that's a huge trigger for me. It takes me right back to where I was six years ago when I found out. That it's the deceit that's the trigger, not necessarily the lunch with a female.
And then she told me to ask my husband what I really wanted to know.
It's so hard for me to open myself up to vulnerability. It has been a lifelong struggle and though I'm better, it's really, really hard.
Nonetheless, heart pounding, I asked: "Are you attracted to this woman?" No. "Is there anything going on that you would not want me to know about?" No.
He insisted, got defensive, said all sorts of unhelpful things about how she's older and more mother-like to him and how he's never sure if he's allowed to be attracted to anyone but me ever again even if he never intends to act on it and on and on until our counsellor stopped him. She told him, pointedly, that this wasn't helpful.
And then she guided him through what was helpful. Reminding me that he's working hard on his issues so that he never again betrays me. Reminding me that he doesn't want to be that guy ever again. Reminding me that he loves me and values our marriage and family. That he won't jeopardize that.
I cried. But then I practically floated out of that session. It empowered both of us. Me to realize that allowing myself to ask for what I needed and opening myself to vulnerability isn't going to always mean hurt. Him to realize that by reminding me that he's NOT that guy anymore is also reminding himself that he's come a long way. That it's a source of pride about who he is now instead of a source of shame about what he did.
Triggers can appear no matter how far we are along the path of healing. And when they appear, they transport us right back to that horrible moment when our world spiralled out of control and we felt alone and scared. Trusting ourselves to ask for what we need in that moment, and our spouse to offer it to us binds us closer together. Triggers can be teachers.