hmmm that's weird. but i forgot ... i think you mentioned in this thread before that you had low iron. you should definitely talk about the diet with your doc then. sounds like maybe your problem is with absorption and not intake, kwim? all this stuff is so complicated, and it's like you have to have just the right balance ... too little isn't good and too much can be just as bad or worse (and sometimes really dangerous)! my dad is having problems with too much potassium right now and is having to totally change his diet.
but anyway, eating low carb *should* result in *more* energy, not less. the carbs only give you a quick high and a crash. also the eating every 3 hours should be keeping your motor running, so to speak.
were you a big caffeine drinker before, and have you given it up? i gave up caffeine once before and in the beginning it was brutal but eventually i actually had more energy and was more alert without it.
best of luck getting this all sorted. and remember, not every diet is right for every body. it's worth giving it a fair shot, but if it's not right for you maybe another approach is better.