I don't know how long you've been low-carbing. If less than a week or two, you may just be going through de-tox. Your seratonin levels should improve after your body adjusts a bit - perhaps in only a few days. Adding a drug may slow your weight loss. If you can avoid it, even with possibly an herbal supplement like St. John's Wort, please do. (Diabetics should not do this without doctor approval, though.)