Instead of going to reddit, I recommend finding a free legal clinic in your area. They are run by well meaning people who actually will listen to you, though it can be crowded and the time short. At the very least they can generally give you advice on basic next steps concerning your matter. I know this is kinda lib advice here, but in lieu of a revolution, it's the best I can give.

(IANAL but employment law cases, especially concerning false positive drug testing are incredibly difficult to claim. All the case law sits firmly in the employers corner with only scant amounts of privacy law protecting employees. Unless you can prove contamination in the screening process, which is difficult and rare, the court will defer to the test and you are boned.)