Okay, first I suggest you read as much as you can about affairs. You will find that most of the time, the spouse and the OW/OM feel they've found what they've been looking for.
My H told me last January, after 13 years, that he didn't love me and we had problems that could not be fixed. Turned out he had OW. He was not willing to work on the M and had no intentions of reconciling.
I got Divorce BUsting and Divorce Remedy and started working on the things in that book. H noticed and eventually came back. Unfortunately in our sitch, things are not rosy and 7 months after returning, he still is having trouble shaking the OW, but he no longer says he doesn't love me and we can't change the problems we had. He felt I would never change, and i proved him wrong and he saw it.
I reommend the book Surviving and Affair. I can't remember the author. But basically it talks about how affairs behing and end. It has given me much peace.
don't give up on your M, but do try ti find yourself and get a life and find ways to make yourself happy without H. Come to a place where you feel you'll be okoay without him (hard, I know... believe me I know). When you get to that place, you'll have more strength to figure out what to do.
I, too, have small kids (2 and 4). I felt very alone when this first happened becuase i was left with 2 kids to take care of by myself. But I figured it out. As far as the lies and deception, BEEN THERE! My H is still doign it.
Take a step back, do some research and take care of yoruself.
I post on the Midlife Crisis boards if you're intersted in checking out my posts.