Am I Overreacting or Overthinking?

My fiancé(M23)(Almost 1 year)together randomly said this to me(F24) TL;DR

“ I don’t know if I should be telling you this or not, but my friend,from High school, pants me in front of a bunch of girls and they were impressed.” No context, that was literally it.Idk how I feel about this. It was weird and kinda awkward.. like why…? Or am I overthinking? I just didn’t know how to react and was kinda in shock I suppose. I did tell him that that was weird and just laughed it off honestly. But hoping to hear what you all think about this and how would you react?