is he cheating?

I need some advice because I kind of don't know what to do. My boyfriend and I have an amazing relationship, it's always been really secure. I was cheated on in my last two relationships so my trust in people is a little skewed but not his. Today he went to the restroom and I was messing around on his Snapchat when I noticed him and his ex girlfriend messaged each other 9 weeks ago (so around late April) but I don't know what the conversation was because it wasn't saved. It threw me back because he had told me he wasn't talking to her since February. Should I confront him about it or drop it since his conversation with her was around 2 months ago? I'm scared of getting hurt again. thank you.