What to do if I have a child support order on file with court system and my ex is currently paying but has not paid back support from 2 1/2 years ago?

Hello.  I am sorry you are having difficulties.  In Minnesota, quite detailed law governs 'old', unpaid child support owed pursuant to a court order.  Such money owed is often termed 'child support arrears' or 'child support arrearages'.  The local child support authority would nearly always be actively involved. Bringing new court action may be advisable depending on the details of your particular situation. Regarding the matters of braces and other expenses, it is possible to make a request for financial support for such purposes.  Each case is decided by a judge (or court referee) on its own merits and based on the totality of the evidence presented to the court.  Regarding Minnesota legal problems such as you describe, I certainly recommend that you confer privately with a qualified attorney about these matters, because typically the help of a qualified attorney is especially cost-effective in situations as you describe. The attorney can aid you typically in being especially persuasive to the court and in collecting and presenting certain evidence. The attorney can help you discern which goals and efforts (on your part) are likely to prove more fruitful. Sometimes it is advisable that there be a time delay of some sort prior to you initiating court action, while in other circumstances it may be prudent to act swiftly and immediately.  If I myself were assisting you, I would discuss the matters with you in great detail.  I recommend you make several phone calls to attorneys in selecting one attorney to help you, because you should feel a sense of great trust with the lawyer you choose.  All the best.