How do you say good-bye to a wonderful husband & father

A little history first: I was 18 just finishing high-school, he was 26 just graduated from college and starting his career. This was 12 years ago.
Over the years we have had our fair share of problems and issues that have been worked out I guess you can say. These were all surface problems though.
He is a good husband, he doesn't cheat, he doesn't stay out with his friends, he is a fantastic father who plays Mr. Mom 4 nights a week while I work the night shift and he loves it. He is completely in love with me, he feels like he is exactly where he wants to be in life with a wife he loves, 2 beautiful children, a good career, an independent career drivin wife, and a modest house. All our friends are married with children as well and we stay pretty busy with get-togethers and parties. He truely loves his life, that is until I turned it upside down.
I actually love my life-style too. I love all the same things he does about our life together, but I'm still not happy. I have no passion or emotional attachement to him. It Sucks. I try so hard to be in love with him, but I'm not. He is a great friend and husband and father, but not lover. I don't mean physical sex, he has always known how to and gone above and beyond pleasing me physically. It's the emotional connection I don't have. It's the emotional connection I have denied I needed for the majority of my marriage.
I have contemplated leaving many times in the past, but my head always won the battle. There are a million reasons for me to stay and only one to leave, so when you weigh the pros and cons it always seemed like an easy decision.
Recently, I had an affair with a co-worker. It wasn't planned, I wasn't looking for it, it just felt right in the moment (then there were more moments). There of course was physical intimacy, but more than that there was an emotional connection. This man just "gets" me. When I'm unhappy he know how to cheer me up and he knows when I just need someone to sit beside me and say nothing at all. Like I said he "gets" me. I had never felt that before. He has also been the person who reminds me the most how good of a man I have and my great kids, and reminds me I have a family to consider. We are still friends and work together every day, but the affair is over.
Since it has ended I have told my husband that I am unhappy, that I wasn't in love with him and that I needed more. He is devistated and so hurt and angry. I have not and will not tell him about the affair. It will only hurt him more and that is not fair to him. He doesn't deserve what I am putting him through right now.
My husband is trying so desprately to fix every little surface issue we have ever had and I'm still not happy, he doesn't get it. I have started seeing a counselor and we are trying to work on things, but I'm still not happy. Every time he thinks things are moving forward he has this sparkle in his eye. My eyes are still sad and filled with tears. Mostly because I don't feel it.
I really want my marriage to work, I really do. I love our life together, our friends and families, and all the little things that go with it. I won't ever find another man who is as good to me and our kids and as commited to me as he is, but I don't feel that emotional connection I need.
I feel so guilty because I keep unintentionally giving him hope that in the end things will be okay, but I'm really not sure. I say all the things I should say "I'll try to work on it, I do love you, but" All these things give him hope, but I'm so affraid of hurting him again and more. I don't want him to hurt, but I don't know if I can continue to feel the way I feel either.
Help!
I don't know how to go about finding out if ther might be anything left or if it really is time to say good-bye so the healing can begin. I don't know what will really make me happy. What if I'm never happy, what if I never find what I need, what if I'm alone for the rest of my life. I'm so scared and confused and I don't like the person I have become.
Any advise would be so appreciated.