Welcome Sissy,
I'm very sorry to hear your story. It sounds a lot like my own in one way.
Have you read my theory about the LOVE TRIANGLE?
http://comeshowme.com/v-web/smf/index.php?topic=74.0It would seem to me that your relationship was based more on each of you needing something from the other and was missing one or more of the key ingredients required for a strong relationship. Once all the children were grown and on their own, the glue that bound your relationship was no longer required or effective, and thus the "sudden" revelation that he no longer loves you. I suspect that since you did love him (and love is blind) that you could not foresee the truth; and that truth was that he never really did love you but simply needed someone to raise his children for him.
It is unfortunate, but that is life. There are takers and there are those who give. The takers will use those who's hearts are soft.
My suggestion to you (if you are asking for one) is to accept the fact that you made a mistake when you married this man; be proud of what you accomplished; and move on with your life as best that you can.
Oh... and a very important part: Try as much as possible not to allow yourself to feel anger or hatred towards him. Feelings of hatred are very counter-productive and hurt you more than help. You want to find inner peace in order to live a healthy life, and you cannot find inner peace if you harbour feeling of hate. You need to understand why. He did what he did because he was unable to raise his children alone and he knew it. At least he was thinking about his children and you can't fault him for that.