So sorry to hear that. I don't think there's any hard and fast rules, everyone is different. It's doubly hurtful if you have a child together but I do vividly remember being dumped by my then fiance days ahead of my birthday with date set and all. I still wouldn't miss the fun of kicking him in the teeth the cheating bastard but then it's been years and I focus on another thought and the memory disappears, or better: it ceases to be important.
Yes, make sure you do talk talk talk to your close friends about it. Have you thought about counselling? I know you probably think you should solder (sp?) on but you have a small child to care for and Lord knows it's hard enough to split from a rat but even harder if that's the other parent and you will always somehow be in each other's lives IYSWIM. I really, really feel for you.
A break sounds great, maybe get him to babysit more (if you can stand it) and go out with friends, go out, out, out. Be among people, do not under any circumstances bury yourself at home! How old are your dc? Are they in school? In nurseryy? Try and get time for yourself, pampering, taking up a new hobby, socializing more.
Do your kids know what's going on? Give them that extra cuddle but make sure your H does his bit, even when he's chasing every girl in town. You don't say why you split, but even men have rebound flings which mean nothing if that helps you. The best, very best thing though is to see him unworthy of any more romantic attention because he'll use it to get things from you (ironed shirts, packed suitcases, sex, etc.) DO NOT BE A MUPPET. It's HIS loss, right! He'll be the one bawling when you find a kind, sexy new man. Yes, it will happen. Trust me!
I was so down, I thought I'd never get my life together again, it didn't help I was overseas and lonely. But it has and it was all meant to turn out this way. Thank your good fortune you're rid of that guy who clearly doesn't deserve you. Someone else WILL come along. x