Whatever you do, don't act like you used to because obviously that is a part of why she dumped you. Just so up and be polite. Not condescending, not ass kissing, not angry, but polite. Treat her the same way you would treat your boss at your job. Polite but also impersonal. If she asks how you are doing or anything, don't attempt to impress her with "how well you are doing" or someone that you have already met. Just tell her you are doing great, working a lot, etc.. something that is nonthreatening to her ego.
She got your child so this bitch literally has you by the balls, not just now but for the next 18 years until this child becomes legal age. She can make your life very very miserable if she took a notion. And chances are she will if you throw some gas on her fire. The fact she is even letting you see your child without a court order is a kind gesture on her part.
There is no promise in the future you will get back together but as it sounds that would not be what you want anyway as she has already shown you that she can fall out of love with you easily. As immortalis said, friends and the gym will get you through this. Just make sure you don't upset her too much and rock her boat because that is going to come back and haunt you.
And BTW, sometimes it is ok to ask questions like this in the AAS forum with the people you interact mostly with and have an idea what you are like so you can get some feedback before it is moved to the appropiate forum. Because the C&C crowd would have been ruthless here.