I think my boyfriend is talking to his ex again but I have no proof

Me and my boyfriend have been together for almost a year. Things have been really good for most of it. He's never given me a real reason not to trust him and I've never been the jealous type. That's important context because what I'm about to say is going to sound a certain way and I need you to know it's not coming from nowhere. About three weeks ago something shifted. Nothing obvious. He didn't do anything I could point to. He's just been a little more protective of his phone. Tilting the screen away when I walk by. Putting it face down when he never used to. Taking longer to reply than usual and then being vague about what he was doing. I wouldn't have thought anything of it on its own. But then I saw a name pop up on his screen when he was driving. Just a notification. I only caught it for a second but I recognized it. It was his ex. The one he dated for two years before me. The one he told me he hadn't spoken to since they broke up. I didn't say anything in the moment. I've been sitting on it for two weeks trying to figure out if I actually saw what I think I saw or if I'm just spiraling. I couldn't bring it up without admitting I saw his notification. And I couldn't ask to see his phone without sounding like I didn't trust him. But I couldn't keep pretending everything was fine when something in my gut had been loud about this for weeks. I realized that staying quiet wasn't protecting the relationship. It was just protecting me from a conversation I was scared to have. The longer I waited the more I was filling in the gaps with my own fears and the story I was building in my head was getting worse than whatever the reality probably was. I decided I'd rather know than keep imagining. Talking it through helped me see that staying quiet wasn't protecting the relationship, it was just protecting me from a conversation I was scared to have. We agreed the best next step was to bring it up without making it an accusation. Not confronting him with what I thought I knew but being honest about what I'd noticed and giving him the space to be honest back. I wasn't going in assuming the worst. I was just going in tired of sitting with something that had been getting louder every day. Whatever he said would at least give me something real to work with instead of the story I'd been building in my head.