How do I get him back ASAP?

Wow... sound exactly like a relationship + breakup that I had years ago... without the kid in the picture though. My advice would be to stay in touch with him, be friends, and soon enough he'll see for himself. Bubbacup gave some good advice, but I'd be really really careful about faking moving on... that kinda shit can blow up in your face big time.
Best of luck.

J

Be yourself. Do not act like someone else in order to be liked - it never works in the long run.Don't hit on his best friend. It hurts your ex's feelings, but some people use it as revenge.Be subtle before you try anything obvious, you need to pick up his signals first. You don't want to look desperate.Tell him you still love him.Be honest with him and yourself. Let him know you want this to work.On-and-off dating can be heart-breaking and even abusive! Always make sure that your intentions for taking him back, or vice versa, are genuine.If your friends tell you that he was abusive even if you don't think so, believe them and do not take him back no matter what!Don't go after your ex if he's married, it will only cause more hurt on your side.Let him know you were thinking about him. Remember that one time you two went to dinner at that great new restaurant and had a fabulous time? Leave him a short email telling him you ate there recently and thought of him. And, by the way, how is he doing? This is a non-threatening way to have a light conversation, and also, a small request for a reply back.

I know you say you want him back ASAP but if you push you could end up pushing him away...
Leave it a while and just occupy yourself with other things (god knows how hard that is but it's do-able).
I imagine that by sharing a child you undoubtedly have to see each other on occasion...so when you do just act as if you're fine and moving on with your life, there's no need to be rude or short with him just show him how well you're doing, then he will see that you're better within yourself and not just for the sake of the relationship.
He knows you love him, he knows how you feel about the situation and as you said you've told him you're ready to try again so there's no reason you should have to keep on saying it.
The ball is in his court and you shoudn't torture yourself while you're waiting for him to return it...
There's nothing you can do or say to make him believe you or come back to you faster, he will when he's good and ready. Any sooner than that and it could put a strain on the relationship from the start. He has to come back with a sure head and a strong heart and at the same time he has to come back to someone who is the same...Sometimes what brings men back to their exes the most is the thought of them moving on and/or the appearance of a new found independence. So you can either fake it or actually get yourself sorted.
How can you make someone else happy if you're not happy in yourself? So find something you enjoy (aside from your child) and leap into it, I have a feeling he'll come home with his tail between his legs and this time you'll be ready to welcome him back into YOUR life instead of feeling like the only place you belong is in his! :o) xXx

I would give it some time before you try to contact him again. Let him have time to think and take some time out your self. It will do you some good to have some breathing space. I know that it hurts but I think it is the best thing to do.

After a couple of weeks, message him by email or text and ask him to meet you so that you can talk. Go somewhere on your own and talk to him. Tell him how you feel, that you have changed etc and find out how he feels. When you talk it maybe worth sugessting/asking if he is happy to take things slow rather than going back in to a full relationship. Take your time, have some fun, spend some time getting to know each other again and remind your selves why you started going out in the 1st place. By doing this it also gives you a chance to show him that you have changed.

I really hope that you work this out. Also say to him that you are concerned and want to work this out becasue of your son/daughter.