I was snooping on his fb messages

I understand it's a sneaky thing to do but he also knows that I do it. But this is what I found.

I'm pretty sure it's someone he went to school with but I don't know her. I ask him everyday how his day was and what he did. He just always says "it was uneventful." When I confronted him. He didn't have much to say. I told him to be straight with me because I don't want to be fucked with. I honestly wouldn't care if he just wanted to catch up with an old friend. Am I over reacting? I'm super annoyed and a little hurt by this. It feels like he's lying to me about something.