I was also twice bitten.
The first time I rug swept it. Big mistake. (I didn't know about SI at the time unfortunately).
The second time was about 8 years later and so I realized I was married to a serial cheater. In her case, it was much more than 2 AP's in fact.
My view is that once you know it's multiple AP's, the odds go up that the 2 you found out about are nothing more than the ones you caught. So you can't rule out more AP's out there.
But in any event, you now have to decide whether you are ok living a life where it's not likely your WW is going to be faithful to you. Maybe she will, but it's just very very doubtful. I mean, she saw I imagine how hurt you were the first time and apparently she didn't give a darn.
I personally made what I felt was a very easy choice to file for D. That's not to say that it was fun or that I enjoyed it. But once I knew she was a serial cheater I knew immediately I had been living a lie and that it was time to move on. We have 2 boys, one of whom has special needs, and so of course that just made it all the more complicated. But nonetheless I was unwilling to share my W with other men. Period.
FWIW I got remarried to a wonderful, faithful, loyal, amazing woman and we now have a daughter together and I have never been happier. I have to say, not spending every day looking out the window to see which way my WW was turning out of the driveway every time she left and trying to sneak peaks at her cell phone to see who she was texting with is not something I miss.
I'm sorry you're facing this same situation I did and I wish you the best of luck and similar positive results.