Gf had FWB relationships in the past with co-workers

Hi. I 26M have been dating this girl 24F for 1 year. We met through work, I started working with this company nearly 2 years ago now, and at the time of joining she had been there for a few years.

There was mutual interest but because of the work place we kept it professional. After about 6 months in, she left for a new job at a different company… so we start texting and long story short start dating.

After about 1 year and a bit of dating we had a chat about past relationships etc and she asked if she could tell me something.

Well, that something was that she slept with 3 guys (and name dropped them) from the workplace and was FWB with them (at seperate times).

To add, I still work at this company and with these guys… so after nearly a whole year of dating (and 2 years working at the company) I’m just now finding out these people I’ve been speaking with have slept with my GF and were FWB.

Am I weird for feeling off about it? I haven’t given her any indication I might be feeling this way, because at the end of the day it’s in the past and love her dearly. But whenever I interact with these guys at work I am washed over with this horrible feeling even after a few months of knowing, I thought it was pass over time. I’m not sure if it’s because she kept it a secret or if it’s because she chose to have FWB relationship with people at work.

I need help to get my thoughts together, and I don’t have anyone I can talk to about it – obviously can’t talk about it at work but also can’t talk about it with my family or friends. It’s also starting to impact our sex life, I’m feeling less inclined to engage. Any advice or guidance would be wonderful, I know eventually I need to communicate these feelings with her so that we can both move forward from it. But I suppose I’m having trouble even thinking how to navigate the conversation or if how I’m feeling is rational.

TLDR: GF had FWB relationships with coworkers and kept it a secret until now.

Thanks