If your ex confessed to taking money from you without your knowledge or consent ten years ago, it could be considered theft or stealing. The legal term for this act is "embezzlement" or "theft by deception."
Embezzlement typically refers to the fraudulent appropriation of funds or property by someone who was entrusted with it. In this case, if your ex took money from you while in a position of trust or had access to your finances, it could be categorized as embezzlement.
It's important to note that the specific legal implications and statutes of limitations for such acts can vary depending on your jurisdiction and the circumstances of the incident. If you feel that this is a significant issue, you may want to consult with a legal professional to understand your options and any potential recourse available to you. Keep in mind that the statute of limitations for pursuing legal action for theft or embezzlement may vary depending on your location, so it's essential to act promptly if you wish to pursue any legal action.