Hi Valerie, it's probably a mixture of both withdrawal from Effexor (one of the hardest drugs to come off on) and new side effects from Wellbutrin. I suggest you give it a couple of weeks and see if these feelings go away....they probably will. I'm on Wellbutrin now and I remember feeling extra anxiety for the first couple of weeks. Headaches as well.
Hang in there and good luck,
Meg