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.
I've got a calorie-counting 'addiction' and am worried to stop it because I know I will end up eating too much. I maintain my weight with 1700kcals + about 85kcals for each mile I run. As a dietitian, do you think it's necessary to count calories? Do you count calories or just go by how you feel? I would find it very interesting to know how somebody in your profession manages their daily diet.
I'm 28 and the 1700 was worked out by an NHS dietitian I used to see (using lots of my food records, weekly weigh-ins and general calorific science type knowledge). And then she told me to eat more on run days.
I think I'll use the extra calories I burn and find a weekly average, like you said.