Why does he praise his ex girlfriend in front of me, when he says he loves me?

Me and My guy friend really like each other a lot , we are so good together , but yet he has a past , he sometimes brings up his ex girlfriend and begins to praise her and talk of all stuff she would say and do . I go mad when I think of all this. He says he loves me but I don't get it why does he talk about his ex and praise her voice and everything else...
Why does he praise his ex girlfriend in front of me, when he says he loves me?
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