I took drug test today and it was positive for tca, i regularly take an otc sleep aid with diphenhydramine. couldn't have caused the false positive?

"tca"????: did you mean THC (marijuana or cannabis)? TCA medically usually means tricyclic antidepressant, and these are actually chemically similar to benadryl (diphenhydramine). If all that was done was a SCREENING test, there are lots of potential false positives, and if used for legal purposes, all screening tests should be confirmed with a more sophisticated test, usually gas chromatography/mass spectroscopy.