Legal matters, unlike other professions, are most often governed by laws and licensing reguations that vary state by state. A lawyer from one state may not provide legal assistance to a client in another state, unless they are licensed to practice in the second state. Since I am a Michigan lawyer I strongly suggest you contact a lawyer in Illinois as soon as possible as this may be a very serious matter. Good luck.
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Child custody/support orders are modifiable/changeable until the child is no longer under the jurisdiction of the court. The party/parent who wishes to change a court order has the burden to prove why the court order should be changed and is no longer in the child's best interests. Based on the facts you reported...what took you so long!? You should consult with a family law attorney as soon as possible.