I am not an addict (my partner is a coke/crack addict). I am, however, on codeine for chronic pain due to chronic health issues including Endometriosis so your post jumped out at me.
Do you not feel able to share your situation with your GP? Or perhaps search out your local drug and alcohol service. They will be able to ensure you do this safely. Withdrawing and tapering off drugs should ideally be done with medical supervision as it is quite dangerous.