hi... thanks for writing.. i have understood your concerns... you have been diagnosed as suffering from major depressive disorder.. the symptoms of lethargy, weakness, dizziness can be the symptoms of depression on which your antidepressant is not working..so whether these symptoms were present before starting cymbalta? if yes then cymbalta is not helping.. if these symptoms have started after starting cymbalta, then they are side effects of cymbalta... if i was your treating psychiatrist, i would go for fluoxetine which is a activating antidepressant drug, does not cause lethargy, tiredness, dizziness..it may cause anxiety for first two to three days..which can be managed with simple anxiolytics.. in my opinion, u shud consult your psychiatrist and tell details about your current problems and follow his advice... i hope this advice will be helpful to you...best luck..