I Am On Tramadol Hydrochloride 150 Sr Tablet 2 A

I am on tramadol hydrochloride 150 sr tablet 2 a day. I was on 200SR a short while ago. I decided last night to reduce the tramadol 150 sl taken twice a day to withdraw from medication. I have only missed one but feel awful. I have a feeling this is not the correct way to withdraw. I have been on tramadol SR for an extended time treating chronic pain. Want to withdraw as it is starting to make me feel sick. Am I doing the right thing?
Sue