To break up or not

Hey girls I feel anxious about something

So basically,

like a year before me and my boyfriend knew each other and dated he had a thing with this girl (they never dated but jsut had a fling) anyway they decided to be friends but he said he probably said the odd flirty comment here and there (before he knew me) bc she’s a flirty person. When me and my boyfriend got together they still used to message but him and his Friends reassured me and just said they were all in the same friend group at school so hung out together and messaged as they were in the same classes and were friends. I said I felt a bit anxious about her so my boyfriend removed her and stopped talking to her. I’m just anxious that they flirted on messafe when we were together?

I’m doubting everything and I feel like I’ve convinced myself that they were flirting on message. I dont know what to do. Do I end it?

Should I worry ?

Thank you