Talking about his ex

So my boyfriend and his ex go to the same school. I use to go to the same school as well but I switched schools. The other day he brought up his ex and I honestly didn't think anything of it, but ever since we've started dating he seems to bring her up about the things she does like trying to talk to him or giving him looks but we were talking on the phone tonight and he brought her up again talking about how she's always giving him dirty looks and he say but it doesn't matter because he's mine. Maybe it's just me being the jealous type but it really annoys me and has me wondering if he still has feelings for her. What do you guys think? I hope I'm just over reacting.