The only time I've only ever felt tired and sluggish or no energy and just over all bleh, is mainly when i'm eating processed foods or carby type foods.  A while ago, I was getting a bit lazy, it was a very busy time, I was eating carbs and got lazy cooking and ate some processed foods.  I felt so run down even though I was taking all my vitamins (I take a general adult multi, B group, fish oil and a powered vitamin C), plus I was having sinus problems which didn't help at all!  I'm back to eating no carbs during the day, eggs for breaky, fruit for morning tea, salads for lunch and yoghurt for afternoon tea and I feel much better and I'm sleeping better.  Probably not much help sorry, but maybe try cutting down on some carbs and upping your protein.  I know that when you do cut down or cut out on carbs you can have a withdrawal process, because carbs are easy energy so the body doesn't need to work as much, but when you start eating protein the body needs to work more in order to get energy out of it.  Sounds like it could be something like that especially if you have had some high energy foods.

Where are your proteins? Little protein in the diet will make you feel crappy. You are not sick because of lack of sugar, it's not like it's a food group. Is there anything else going on in your life which could contribute to this feeling of unwellness? Sometimes if we are mentally drained our body ends up taking a battering.