I'm so sorry this happened to you. I hate to hear stories like this. 8 years is a long time. Makes my heart sink. I know how it feels to be cheated on multiple times. Very awful feeling. My heart goes out to you. You are a strong and brave person to pick yourself up and keep moving forward. It's good to vocalize this stuff so can grieve the loss of a relationship you thought would survive. Let it out so you can heal.
I know too how damaging it can be to your self esteem as well. You can't hear enough how beautiful, smart, and loving you are. You need to tell yourself this as much as you can. Do things that will build you up.
Take care!!