I would suggest that you try to find a good counsellor that you can talk to about this. It doesn't seem to be a major life crisis at present, so you have time to find a really good one, who is experienced and you click with.
One other thing, are you going through a life changing event at present? Eg. childbirth, marriage, divorce, bereavement? Because that could be bringing it back to the surface. Or maybe one of your children is reaching the age you were? Or have you visited the place it happened?
You don't have to answer these questions here, they are just ideas for you to ponder.