My sister took venlafaxine (known as Effexor in the US) and had withdrawl when she tapered off. I have heard similar stories from other people. Effexor prevents reuptake of two neuro chemicals in the brain - serotonin and noradrenaline - whereas many antidepressants only prevent reuptake of serotonin. I think that is the reason the taper is more difficult with venlafaxine, plus you were on a fairly high dose.

Perhaps seeing a psychiatrist would be helpful in this process. I am sorry you are experiencing this.