I take fluoxetine at a high dose and have had no problems with energy. But I know for some people it can cause tiredness to begin with. I'd give it another few weeks so your body can get used to it. Antidepressants' side effects don't usually continue (especially with newer ones, like fluoxetine). I've tried my fair share and fluoxetine had no bad side effects. One thing I've learnt is to give them a chance to work before giving them up. The first week or so will always be the trickiest because your body hasn't had it in its system before.