how long does it take to stop withdrawing after u stop taken methadone?

i have been of methadone for 6 weeks yet i still withdraw, i have been on 150mls and cut myself dowwn to 20- mls over 2 years. The last 20mls i cut down 1ml a week till i got to 5mls, then i just stopped.

: http://alcoholdrugstreatment.info/how-long-does-it-take-to-stop-withdrawing-after-u-stop-taken-methadone