The best way to keep yourself out of jail is to pay what you can towards the back support you owe. If you have not already filed a Petition to Modify Child Support, you should do so immediately so the arrears do not continue to accumulate.
You should consider hiring an attorney to help you with this issue.
Making as large a payment as possible toward the arrearage is always helpful. Frequently, a court wants to see a big lump sum payment made, and usually it's even better to have the payment made either prior to the day of court and to bring the money with you to court. A cashier's check or money order is usually best, because the parent who is owed the money can be certain that the funds will clear the bank account. If you pay by any means other than a check, it would be wise to get a receipt.