I've never taken that drug, too afraid of it, but it targets norepinephrine receptors as well as serotonin, and the former is basically adrenalin. So you've stopped taking a very stimulating drug, which might have slowed your metabolism. I would assume that if you successfully quit this drug eventually your body will find it's natural weight again. In the meantime, you might consider taking adaptogenic herbs that balance the adrenals, as this drug has been working them hard, to see if that helps.