First, don't stop paying her but do go to child support and have an order drafted that shows how much you are required to pay. As the other person stated, everything you are paying right now is considered a gift. Don't stop giving it to her though because then you are not showing you are interested in taking care of your child. If child support orders back support, hire an attorney immediately. They can show you have been paying and cancel out your back support. It is almost impossible to fight child support on your own and win though.
You need to file for joint custody immediately! You should be entitled to your child just as much as she is.
Just a tip, stop complaining about what your ex does as far as money. It makes you seem childish. I know where you are coming from and I completely understand, but courts don't like to see that! Also, you need to try to be cordial with her because you two will be spending the rest of your lives as a family, even though seperately. If you two can't get along the only person you hurt is your child! He doesn't deserve that.
PS- when you want to convince people you are the better parent, you might want to consider a better screen name, lol, that looks pretty bad!
Best of luck to you