SUBREDDIT: r/relationships
TITLE: I (23F) found my Significant Other's (21M) porn.
POST: Okay so I guess I really should have known this would happen someday. I knew he watched porn. I don't particularly like it, but I don't consider it cheating and I'm not going to attempt to make him stop. 

He had forgotten his Nintendo 3ds with me and I opened it up and was poking around. I opened the Internet browser and bam...porn everywhere. I was surprised because I didn't really expect to find it on a 3ds.

So, knowing what he likes to watch on his own time is a little weird for me. I have some self-esteem issues so my mind quickly started comparing myself to these girls. That mixed with the guilt from looking through his game system without his permission, and I'm feeling like a mess.

How do I tell him about this? I feel like I'm not going to be able to just forget about it and act like I never found it. I don't like the thought of hiding this from him.
TL;DR: 
I looked through my SO's 3DS and found porn in the Internet browser. How do I tell him about what I've done?