Grieving a spouse who was unfaithful

I’m so lost and incredibly hurt, my spouse passed away recently with cancer. 3 days prior I gained access to devices. My daughter found there was multiple instances of infidelity, multiple people and in particular one person I assumed had my spouse survived, this person was going to become a significant partner in their life. I don’t know how to get over not only the betrayal, but the fact that my daughters now have that horrible memory. My heart is hurting so deeply, I don’t know if I even knew them at all, this after nearly 30 years of marriage. How do I navigate life now, I’m so broken.