When people have been together for such a long time the love changes, especially if there are kids as well. Most people fail to adjust to the changes. However it is not suppose to be that way. I am failing to believe that you don't want to be with him anymore because if that was the case you would have not went back to him for all these times you walked away and came back, I know you said you were doing it for the children but were you really doing it just for them? What I know is once a woman feds up she goes and never look back. Try to find ways of bringing back the spark you too had before and believe me it is possible.