I'm having some difficulties with my marriage at the moment, and I needed to talk to someone as its chewing me up so much, me and my depression cant handle it anymore.

I'm happily married with an amazing, supportive husband. Recently I was at the gym and discovered an ex who i havent spoken to in a long time also works out there. we said a breif hello and that was it. later that night he messaged me on facebook and after some general chit chat, the tone of the conversation turned to our history, and some fun times we had sexually. he expressed some wishes for things he would have liked to have done in the past and i told him he shouldnt have been chicken and shouldve done them.

my husband read this exchange in my facebbok messages and wants an answer as to why i had this conversation. the bit i'm struggling to deal with, and that my husband cant understand, is that i dont know why i did. i love my husband unconditionally, i am not attracted to this ex, nor do i wish our relationship had gone further. i have no desire whatsoever to cheat on my husband at all. but my husband wants answers, and i dont even know what those answers are myself.
please help!