My fiancé cheated and I don’t know what to do

For a little backstory. My fiancé F29 and myself M29 have been together since we were both 16.

It started back in 2021. I discovered at her sister’s wedding that my fiancé, then girlfriend had been cheating on me with a customer at her work. We went on a break which then I found out she slept with a co worker not even a month after we went on our break.

After some time we decided to give it another shot and we moved in together. It is now 2025 and I found out that she has been sending pictures to the same co worker she slept with back then. I want to leave but my fiancé is now pregnant with our first child I’m afraid to make things messy for my future kid. I am not sure what to do. I still want her in my life but I have lost all trust in her and faith that this will work