I saw on my girlfriend's phone she was sending dirty text messages to some guy?

We have been having relationship problems for the last few months. We haven't had sex in a few months. She says she loves me very much and cares about me.

She always has her phone with her and she texts up a storm where I cannot see. This morning she went to the bathroom and her alarm went off. On her phone I saw some cyber sex back and forth between her and some dude.

Do I confront her about it? Do I bring it up? Do I investigate some more on her phone?
Updates
+1 y
Should I get more evidence to be sure she is?
Updates
+1 y
So I got more info, he is a guy at work with kids. He says "love you" but she doesn't respond
I saw on my girlfriend's phone she was sending dirty text messages to some guy?
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