I'm with Cindy.

If only for curiousity I would track down first affair woman and find out what he was like with her. I'm just so curious why he married you when, it, wasn't there and he could have had her???

But, if you don't care about the curiousity, then I would decide if you want to stay in the marriage simply for economic reasons and for the kids.

In that case I would find a lover of my own, put money away for the day the kids are out.

Your H sounds like a narcissist. Here's some links:
http://www.operationdoubles.com/narc/

I also would get a PI and find out what he does during the day.

I know none of these are standard dbusting...but they are 180's aren't they?