I was on Zyban for the same thing and went psycho about a month into it!!! I never stopped smoking on it either and I stopped taking the pill after a month. I couldn't take the feeling of my insides getting all twisted and tension and then me flying off the handle over the silliest things. My husband was deployed at the time so it wasn't far that my daughter (5 at the time) was the center of my lashings.
A few months ago my Dr put me on Welburtin for light depression. After a week I had dry mouth so bad I'd wake up in the middle of the night with my tongue stuck to the roof of my mouth!! And I could feel the tension building up again too. I talked to his nurse who said to keep taking it because my body would adjust to the stuff and the side effects would go away!! I stopped taking it cause I wasn't going to go through the fits of rage like I did with the zyban.
What finially worked for my hubby and I to stop smoking was Chantix. We didn't even finish the first 6 week program and it will be 3yrs come Oct that we stopped. We were shocked when it got pulled off the shelves for a while do to people's mental health. We never had any issues like that but I do know that some Drs here were prescribing it along with Zyban, Welbutrin, nicotine gum or the patch and you aren't supposed to do that. Just take the pill and nothing else. A friend of ours is using it now and two weeks in he said dog poo smelled better than cigarettes!!
IMO i'd stop taking the Welbutrin. To me, no anti depression drug should cause a person to feel like I did and like you do now!!! This is the side effect of the drug and NOT from stopping smoking!!!
Good luck with stopping smoking!
S.