I'm on a whole host of meds right now, one of them being Wellbutrin. For a short time, each added med would give me a boost in mood, but then go back to where it was. So, when Lamictal was added last month, my pdoc cut my Wellbutrin in half. About two weeks later, I was crying uncontrollably...about nothing. I was crying in the shower, crying at movies, even cried at a party I went to.

And it was the kind of crying I couldn't stop.
So I put in a call to pdoc and he went back to my original dose of Wellbutrin and the crying went away almost immediately.
I agree that without going off meds with your Dr's advice and slowly, it may "seem" like everything is ok....for awhile.