I am weaning off Effexor by reducing the dose by 37.5 mg weekly. I am on 150 mg now and if things get tough I will slow down. Looking at Wellbutrin down the road.
I feel like you should have weaned down the Effexor a bit before adding a drug in a different category. Effexor is a SSNRI, Wellbutrin is an antidepressant of the aminoketone class.
JMHO, I wish you luck.