Hi, I just found out that my partner slept with my friend. It happened over 25 years ago and at the time we were on a break. I feel really shit and I don't know what to do. I love my partner and want to stay with them, but the thought of them together is too much. Obviously the friend is gone from my life and unfortunately I'll probably leave that whole group of friends. I'm so sad, my partner isn't who I thought they were. How can I move on?