Been there done that even got the crappy T-shirt to boot!
I say this only because I was in your shoes September of 2010. It's now August of 2012 and I sir am a better man than I was then. I had one adopted son and 4 foster kids, brand new house, cars etc. All taken away.
It sucks like nothing in this world. The hurt can't be explained at all. Eventually you will get over it. But no matter what anybody says right now you will think we are full of ****.
Best advice I can give you, stay off the booze, stay off the drugs and do not bash or talk crap about your ex in front of your son. 20 years from now your son will look back and know who the bad person was and you won't have to explain why you treated his mom like crap back when.