Betrayal trauma - healing advice?

Hey all,

I guess healing / recovery comes in stages, I found out my ex-partner of (would of been 4 years tomorrow) was having a workplace affair with another woman who was also in her own long-term relationship. I found out from reading her chat gpt confession, where she confessed they were 'falling for each other' and didn't want to distance herself from the AP as she can 'compartmentalize'.

I do understand trauma comes up in strange ways and I have been very good at accessing my anger more recently, but for some reason (maybe because our anniversary is tomorrow) I keep thinking about her having this affair, especially when I am at work - I just wonder how she was able to do this and lie and gaslight to me about it for months, when I suspected something was going on. Even saying 'look at my mum, do you really think I could do that!?' - her Mum has cheated on her Dad for years and is a master liar / manipulator.

Can anyone who has been through an affair / betrayal trauma please advice the best way to deal with thinking of your ex with the affair partner, my body keeps reacting badly to every thought, its very hard and makes me feel sick. I guess this is quite normal, as it's still quite raw .. she started distancing herself from me / lying to me from late January until end of March, when I found the chat gpt confession. During this time she was isolating me out of her life, and made me feel like I had done something wrong - telling me she had a decision to make basically about our relationship - I was wondering for months what I had done and if we would even stay together, the power was all in her hands.

This is so hard to manage, please anyone shed some light please or words of wisdom.

Thank you all SO MUCH!