Myrrh - here's my take - there are two kinds of WASs on the boards. The vast majority simply get depressed or have midlife crises and succumb to the "myth" of "falling in love". Usually they will feel some guilt or regret at some point, and they definitely can come around - my H is proof.
But there's another type of WAS - the serial adulterer - who just plain has issues with fidelity. This is a surprising minority of the spouses on the board, and I think their problems run much deeper. Maybe it's a character disorder, or a personality disorder, or a sex addiction, or whatever - but it runs deep and isn't going to be fixed without a LOT of therapy and hard work.
Now I'm just guessing about your H, but I'd say he falls into the second category. I mean, the "Type I" WAS, when faced with a pregnant OW, would generally either come running back to his W, horrified at what he'd done, or convince himself that it was "true love" and he had to leave his W (if only to justify his actions). Taking up with ANOTHER OW and letting yourself get caught by the pregnant OW - those are the actions of the "Type II" WAS - the disturbed serial adulterer.
Given that, you have to ask yourself what it would REALLY take for your H to convince you it was safe to risk your future (and maybe more children?) on him. I'd say, nothing less than a year of intensive therapy and perfect behavior on his part (including a complete "open book" policy so that you could be sure he wasn't hiding anything from you) before you'd even consider having him back would be wise. I know it is really a drag since you have a child - but your child is young enough to still have a chance to grow up bonded with a really great stepfather if you can find one.
