1) Look FABULOUS all the time. It doesn't hurt to let him see how cute you are.
2) DO NOT CLING. Look happy and independent. Right now he needs to start worrying about losing you, if you pursue him then that thought will never enter his pea-brain.
3) If he is taking the kids to do something on his own, make sure when he picks them up that you are dressed up, with perfume, as if perhaps you were going on a date, and that you leave the house when the kids do - I don't care if you get in the car and drive around the block until he leaves, but just make it LOOK as if you might be going out on a date or dancing with girlfriends. If he asks you where you're going, give some vague answer ("Meeting a friend.... No, no one you know"). What you need is plausible deniability (that is, you really aren't dating or doing anything untoward) but leave enough mystery that he could IMAGINE that you might.
4) Be cheerful, upbeat, fun, sexy, flirtatious - it's ok to show him what he's missing.
5) At some point, I'd consider asking him point blank if OW is pregnant. If she's not, the question might just introduce some fear into his thought processes (because right now he's in fantasyland and hasn't thought that far ahead). If she IS pregnant, the sooner you know the better.
