Veronique,
Being 40 myself and after reading your post I really don't feel you are having a mid-life crisis. You are just unhappy in your marriage, which in a lot of cases can lead to having an affair no matter what your age may be. You had an affair 15 years ago, and you weren't in mid life at that point in your life.
You should never leave someone for someone else. If you are not happy with your marriage than base your decision on that and not on the fact of pursuing another relationship. Then on that decision and after ample time you can start pursuing other relationships, or better yet the right ones will just happen, but simply just seperating to see if something else could work out, is never a good idea, and is not fair to your husband, since it seems he is a saftey net for you.
One thing for sure, you deserve to be happy, search your heart and if you don't think your husband can make you happy, it is only fair to yourself and him to allow yourself to experience the greatness of a fulfilling relationship.
The fact that you have always thought of others when making love to your husband pretty much tells that you are not in love with him and possibly have no chemistry with him at all, which is imperative for any relationship.
I have been through a lot myself and most of what I speak of is from experience. When I read your post I could relate to some of the things you had mentioned and felt compelled to comment. (I usually don't post on forums) I hope this advice helps. Good Luck!
