M.R.
Was this for post partum or PMS related issues? If not, I would suggest that you visit a psychiatrist. They are truly the best at prescribing these medications and know what side effects you can expect. Weight gain is much more of an issue for antidepressants than weight loss, so you have a great many choices if that is not an issue for you. Why you would be prescribed one with that side effect is beyond me, more reason to see someone who specializes in these medications.
M.