I Have Been Given A Rx Called Desoxyn 5mg. I

I have been given a Rx called Desoxyn 5mg. I don't take it on a regular basis,however I took some before a Dr. Visit which happens to be my Pain Specialist for Chronic pain. Now they want to discharge me from the practice because he said my urinalysis says<500 for methamphetamine. Because I took this medication would this make my UA show this. I feel as though he has labeled me as a Meth Head. I follow my instructions to a T as prescribe