I need help

I started taking Pseudoindoxyl back in October. I have stopped it a couple of times but do to bad back pain I have been using anywhere from 15mg-90mg at most. I would say average with be 45-50mg per day. I have to take a dot drug screen in a couple weeks plus I want off this shit. I just want to feel better without this stuff. I’m starting to go down on dosage. I only used 15 mg yesterday. Today I have only used 7.5 mugs so far. How long should I taper before CT. I can’t chance failing a DOT drug screen either. Please help. ☹️😢 When with withdrawals be tge worst?