@terrimindy, there are some medications which can give false-positive readings in drug tests. Metformin (Glucophage), may result in a positive test for amphetamine or methamphetamine, according to drugs.com.

Here’s a full list of the meds which can cause false-positive readings.
https://www.drugs.com/medical-answers/medications-false-positive-methamphetamines-3566578/
That has to be incredibly frustrating for you! If this is for work, your urine samples can sent to a lab for a more advanced tests which would show the presence of Metformin. You also can go to your doctor who prescribed meds and get a letter to keep on file at work confirming that you are on Metformin for diabetes. I hope you get this all sorted out.
Is this for your job with routine drug testing?