You need to file a motion to enforce, which can be done without an attorney through a federal child support enforcement program.
Federal Child Support Enforcement Handbook for Non-Custodial Parents
To learn a father's rights, join Dads House in Yahoo Groups. It's free to join, access all materials, and you associate with other fathers going through, and have already gone through, the same issues. We have an Educational Manual that teaches everything that needs to be known in addressing your legal issues. Mention your question here when asked why you want to join, as well as your state?