My bf called me by his ex's name

I (18F) and my bf (20M) have been dating for a couple months now, although we've known each other for around 6? We were having a sleepover and I went up to go to the bathroom, when I came to lay back down he rolled over and hugged me and said "I love you (ex's name). He then said "wait what's your name?" And started going through different names that start with the first letter of his ex's name before finally landing on mine. He normally says nonsensical things in his sleep as he is a sleep talker but hearing him say he loves his ex felt like a lunch straight to the gut. I don't know how to bring this up without feeling stupid or getting emotional because that really did hurt. I have some of my own jealousy issues I need to work through and I recently also found out who this ex is due to some mutual social media followers, so thats making it worse too. I just feel stupid for being so hurt by this but I also am upset at him for calling me that. It's making me think that he was thinking about her or dreaming about her. I know that whenever he sleep talks it's because that's what he's dreaming about in the moment. He's said some stuff about him being at work then opening his eyes and going "oh I was dreaming that I was at work" or "I had a dream you were doing this" and things along those lines, so this just makes me feel like he's thinking about her. I don't know what to do or how to bring this up in a way that will make the conversation go in a direction thats productive because it really did hurt me.