I took a urine test the other day and tested positive for opiates and methamphetamine. Why?

I am Female, I have type 1 diabetes, Hepatitas C, and siezure disorder. I am on insulin, topomax, prozac, zelnorm, zantac, lasix, klor-con, albuterol, ultramm, a multi-vitamin and an over the counter diet pill. I eat normal foods, and drink alot of diet coke, Propel water and green tea. I take over the counter pain meds and sinus meds when I need them. Can anyone give me a clue on what could be causing these results?

: http://alcoholdrugstreatment.info/i-took-a-urine-test-the-other-day-and-tested-positive-for-opiates-and-methamphetamine-why