Thank you for your query at DoctorSpring.com
I understand your concern.
If you have not used any drugs in the recent past, say 2 weeks, then there is no way the test can be positive. Sometimes false positive results can arise due to use of some other drugs like medicines for cold ( Phenylephrine ) or some psychiatric medications such as Adderal. However without any drug history, this is false positive. Amphetamine is an external compound and our body does not produce any.
Feel free to discuss further,