If a final order has been entered in your case, no matter what you and your ex-husband decide on separately, that will not be binding, nor legally enforceable. Depending on how soon the order was entered, there may be time to file a motion to set aside or motion to modify, and possibly request a new hearing, for example. It sounds like neither you nor your ex-husband were represented by family law attorneys. I strongly advise that you speak with one immediately.
The answer to your question depends, in part, on what "papers" you are referring to. If the judge issued a final order, then there is nothing for you to sign. If you reached a mediated agreement, then you should have had to sign the agreement prior to leaving mediation. There is no requirement to sign it again.
Once an order is granted, that order is binding. The parties can reach an outside agreement, but that outside agreement will not be binding or enforceable. Therefore, if either party stops abiding by the terms of the outside agreement, there is nothing that the other party can do about it. If the court has not yet issued a final order in your case, it would be in your best interest to attempt to have your outside agreement made into the order of the court.
If either of you has an attorney in the present case, you should contact that attorney about having the agreement made into the court's order (assuming one has not already been issued). If neither of you is represented by counsel, you may want to consider contacting one right away for assistance.
I hope this information helps answer your question(s).
~ Kem Eyo
The above answer is a general explanation of legal rights and procedures. It does not constitute legal advice. Nor does it establish an attorney-client relationship between the individual posting the question and the attorney providing the answer.
I agree with my colleagues. Speak with a family law attorney immediately to see what options you have. For the future, try to work it out between yourselves rather than going to Court because, many times, neither party is happy with the outcome. Good luck with this issue.