Can you show positive for amphetamine doing a drug test if you dont use drugs with amphetamine in them?

It depends on the type of drug test used. A urine test, the most common, can give a false positive because the test does not test for the drug per se but it tests for metabolites of the drug. As a general matter, given a modern test and a reputable lab, false positives are rare. At the time of the test inform the tech of any OTC, herbal, prescription meds you have taken. Any positive urine test, moreover, is re-tested by spectrographic analysis, which is considered rock solid. Check out NORML.org/drug testing.