My doctor once prescribed Paxil (paroxetine) for my depression but after a couple weeks I asked him to put me back on Zoloft (sertraline) as the Paxil made me so fatigued I couldn't do anything - no ambition, no energy.
If your antiD isn't helping, ask your doctor to try something else. If you've been taking this med for over six weeks, then the fatigue is likely not a side effect, as most side effects go away after a month or two.