No, you do not have a defense. There is no defense for DUI for "necessity"--for feeling that you had to drive while intoxicated. Even if you were trying to get someone bleeding from an injury to a hospital, if you were intoxicated at the time, you'd be charged with DUI. The law expects you to do something other than drive impaired--such as, in your case, calling the police (calling 911) when your ex showed up at the club. The officer did not need to take your situation into account, and a judge does not, either.