<human>: He's always been a Redditor and we usually go on together; about a week ago he was Redditing on his phone but wouldn't show me what he was doing. I noticed it was a different username than the one he normally uses. I searched it later that day and he's made a bunch of posts on r/dirtypenpals (a NSFW subreddit; it's basically a bunch of people looking to talk dirty online/send nude Snapchats/whatever). He's been asking to roleplay scenarios, message girls, asking for kiks/snapchats, and just talking about different sexual fetishes.

I did a bad thing.

I know his passwords so I logged in as him. He had over 50 messages in his inbox: nudes, Snapchats, kiks, dirty messages. He even made a separate Snapchat username.

I am devastated. We have had a very happy, healthy relationship and our sex life is not lacking in quality or quantity. We're both college students and we spend plenty of time together; I have never been worried about anything like this before. He has also never communicated any of these sexual desires to me before and I am wondering why.

What do I do? Do I admit I was being a creep and ask him about it? Do I hope it just stops? If this is going to continue I can't stay with him.

Provide a brief overview of the text.
<bot>: Boyfriend is sending sexual messages to girls via Reddit but I found out by being semi-creepy, previously happy/healthy relationship is in jeopardy.