What Causes False Positive For Methadone In A Drug Test?

im on fentanyl 100, Percocet, Ativan, flexeril and a generic benedryl allergy containing antihistimines, what causes me to get a false positive for methadone? The doctor is about ready to kick me out of the program because of that.. Please help me... Thank you OMG, NEVER MIND. I WAS HOPING FOR HELP BUT CANT PAY THE MONEY.. NEVER MIND. THANKS THOUGH....TAKE CARE