Do I confront him?

I'm gonna sound crazy and maybe I am...but my  husband and I have been together for 3 years, and today I was on his computer and I found a letter he wrote to his ex - last year. Now during that time I remember we were going through some things, and it was a really dark period for me, but in this letter he wrote how he'll always love her and everything that he does is for her. I felt sick to my stomach reading it. We haven't had any issues since and we've honestly been so happy. I know it's my own fault for snooping. Do I own up and ask him about it, or do I try to pretend like I never saw it?