Fiancé talking to someone he used to hook up with

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Is it okay to text someone you used to hook up with but didn’t date? I saw on my fiancé’s phone that he commented on some woman’s Snapchat story. I know he used to have sex with her because he had a picture of her pu$$y saved on Snapchat. I didn’t get mad about that because it was from months before we started dating each other but I still don’t like that fact that he still has her there and he sent a message to her. I have people I slept with as friends too but I never talk to him, especially inoculate a convo. I’m surprisingly not very bothered by this but it’s still m uncomfortable:/