I Just Had Results From A Pee Test , Doctor

I just had results from a pee test , doctor said It came back positive with cocaine , I have never used that stuff at all , I work shift work and run a crane , many other people use that crane as well , at work there is a few different chemicals we use on are product , but I have never ever had a positive reading before , I do have a bad habit of biting my finger nails , I am beside myself over this , I was truly set back and very upset about this ,