Can a urine test be used against me in court if the officer did not read me the Miranda rights?

On the street, he said that I was under arrest, cuffed me and put me in the car. Although his main concern was drugs, he did not search me and briefly searched the vehicle. He found nothing. Even though I was driving while revoked, could not show any proof of insurance, no title, or registration and he parked the car himself. When he cuffed me, he said I was under arrest, but did not read me my rights, and when I was in the car he said it was a hold and release and then made a comment about how he parked the car legally. I could go get it later. At the station, he just read me the implied consent information. I took the urine test, was placed in a holding cell, after which a family member came to get me and they let me leave. If I was not really under arrest, not read my rights or held overnight, was I even under arrest and is the test admissible in court? I have no prior drug related issues, or arrests, no probation or parole, and other than a few driving tickets, no record at all. I can't afford to pay a lawyer so I have a court appointed lawyer who does not believe me, cuts me off if I try to ask or talk, even went so far as to call me crazy and said that I’m claiming to have been tricked into consuming drugs would never be believed in a court of law. He even asked me why I didn't tell the cop I was high, and that someone tricked me. This happened a year ago, and instead of letting me have my due process, he insisted that we wait for the Supreme Court ruling on urine test admissibility which at the time was in my favor. I have no real options but to plead guilty now, and at 52 years old, mentally ill and disabled, it’s hard for me to even think I will have this on my record. I have a million questions and a viable reason for driving that night, but he says only the facts and the facts are I was high, driving illegally and got caught.