Thanks for your question.
Fortunately i am a psychiatrist
and a deaddiction specialist,
Codeine is a opium group of drug having high addiction potential.
You should know why a person addict to some drugs because when they leave it there are withdrawal symptoms
to neutrilise those symptoms that person again go to take the drug.
Its good that you want to leave the habit.So for that better thing to admit in any deaddiction center.
As you know when you leave the habit all on a sudden you have withdrawal symptoms like-insomia,lacrimation,diarrhea,piloerrection,dysphoric mood, mydriasis
,yawning,autonomic hyperactivity and that can be manage by giving antidote or clonidine
and after overcome of withdrawal symptoms you have to take one opiod agonist for replacement for prevention of relapse.there are so many drugs for that.I can not name those in this forum.
Side by side psycho education and counselling
should go that is called relapse prevention counselling or RPC that help you to avoid situation which provoke you to take drugs and also to control yourself during craving.
Psycho education of the family member also should be done that how they behave with you.
For the whole thing you need to be admitted for 4-6 weeks and you become free of codeine and will be able to lead normal life.
By the way your personality changes are due to drugs and depression
is also due to codeine .It is called substance induce mood disorder
.When you will leave the habit you mood and personality become gradually normal.
Dr Sourav Ganguly