I can't interpret exactly what is going on in your case. One possibility, though, is that the amount you are paying is not what the contempt hearing; or you have been paying the other parent directly and the court has no record of your payments. Given that your liberty appears to be at stake, you certainly should hire a lawyer.
This answer is for informational purposes only. By answering this question, no attorney/client relationship is created. Although the legal information is accurate, it may not be appropriate for your situation. The best way to handle any legal problem is to seek the advice of an attorney.
A commitment hearing normally means that there is a continuing contempt finding if it is related to child support. You need to contact an experienced family law attorney right away to assist you in this matter.