Working with bf’s ex fwb. How to handle?

My (F30) longterm (2Y) partner (M35) and I work in the same big corporation. He has disclosed all his past partners to me, including those from our common workplace. None were serious, just some kiss, and then one friends with benefits briefly before me. It was truly a ‘business agreement’, no feelings, no activities together except sex. They started before she came to work there, and just continued as she started working.

The deal is, now for me it is disgusting. We also work together (but met outside of work really), but i have to see this ex fwb daily. I am not jealous of exes and whatnot, except this one is bothering me. Im not intimidated (i honestly find her so unattractive). It’s about my ego, i know. Someone from work knows my life partner intimately, knows how he looks like naked, has been to OUR home etc. And as shallow as it is, how could he hook up with someone that unattractive (he also doesnt like her, really just had needs caressed)

Our relationship is amazing, it is really the only problem that keeps coming up (from my side). And its so unfair, he cant change what has happened. He has said that if he knew hed meet me, he would have never hooked up with her. I have managed to make peace with it, even be in the same group without being triggered. But then it comes back again.

The past is past, i cant hold it against him. Well what about when the past is in my face daily?
Does anyone have similar experiences and how to handle it? Positive experiences please, how to focus on the future, how to ignore some random unimportant past hookups you have to see daily.

I hate to be ruining something so amazing, he is perfect to me. How do i get over this, handle it, face it?

Tl,dr working together with long term bf’s ex fwb, see her daily. How to manage being triggered? Relationship is great.