Hi op I really feel for you as what shines out of your post is that you have felt starved of love for years. This will have a terrible effect and make you really vulnerable. We all need to be seen and recognised and able to be ourselves- that’s what you’re getting from this man at work and it is hugely powerful.
For the moment I would take this as a wake up call to look at your marriage. Is it saveable? By which, I dont mean- is it bearable? I mean, can you bring joy and hope and friendship and great sex back into it?
If your conclusion is that you can’t, have a think about how the split would work in legal and financial terms - money, kids, house. Get a half hour advice from a solicitor outside your work (don’t rely on your colleague).
Then think about the realities of leaving- practical, emotional. What would be difficult? What support can you access? How would you feel being by yourself on a Saturday night? What might make you feel better, if this would be hard? Where would you like to live? What would you like your new life to look like?
I’d put this man to one side for the moment, because he’ll still be there in a year’s time. Maybe he’s the one for you, maybe he’s not, but if you get involved now you’ll be doing so from a position of great emotional vulnerability and handing him a lot of power. You can take a bit of time to build your strength.
It does happen- my father left my mother for a colleague, and they’ve been together for (ulp) over 40 years. I left my ex - I won’t lie, at times it was difficult and frightening and lonely, but now, years on, I’m happier than I’ve been for decades, and so very glad I managed to find the courage to go. Divorce doesn’t need to be frightening and bitter. Sometimes people just move apart, and then they need to find a way to end things with respect and kindness. Maybe your husband could even find a woman who wanted to be with him, as opposed to sadly enduring him for the sake of the kids!