Boyfriend brought up old problems

So my boyfriend brought up an old situation that happened in his previous relationship his ex had been sexting his best friend they sent nudes all that but he brought it up today randomly just talking about how he found out who his real friends were &’ idk how I should feel like is it that he wants the ex back or is it that he really can’t believe his friend would do that to him &’ still lie about it . He says he loves me he literally comes to see me randomly he calls randomly he’ll text me you know he’s a great boyfriend hasn’t given me any reason to doubt him at all but this argument is so confusing this isn’t the first time he brings it up either ... am I a distraction at this point