My boyfriend still looks at his ex's facebook profile?

[Vivi]

My boyfriend and I have been with each other shy under 3 years, we spend almost every day together and I love him very much. I found out he has been looking at his ex's (more like, he liked this girl while we were dating, and when we took a "break" he had kissed her about 2 years ago) facebook profile recently. I think I'm maybe overreacting a little, because he says he loves me and thing's have been the same like always. But I feel very betrayed and hurt, I thought he had gotten over her. He has told me countless times he was over her and that he didn't even care about her existence anymore. I don't want to go crazy on him or tell him off, but what is the right way to confront him maturely? Does he still like her? Is he not over her?
I'm so confused and hurt. Please help.