Stop torturing yourself as it serves no useful purpose. Skip the confession as you wrote that he'd freak out and that you had no solid commitment at the time. Don't fret over what happened as it was part of your single life back then. All that matters now is whether or not you feel this b/f is the one who/whom you love.
Don't get your head into this misguided state-of-mind where you feel you must tell him everything. This ONS should be part of your past. Just make sure there are no more one-night-stands. Guilt (and jealousy) are wasted emotions which serve no useful purpose.
Also, I have a sinking feeling that there is a certain amount of control by this guy. Does he have an anger problem? Are you feeling fearful?