From my experience Lithium deals with mania and not so well with depression. Maybe that is why you are on another mood stabilizer that is supposed to deal with you depression. I would have a frank discussion with your pdoc about each med you are on and what they are for before making any changes. I am nearly 5 months into a deep depression too and even ECT hasn't shaken it off, though it did bring some relief. I feel for you and hope you see brighter days soon.