I had the same thing.. felt fantastic for the first 6 day**** the wall for about a week, tired, occasionally dizzy, especially first thing in the morning.. by the afternoon I'd start feeling ok. It passes, I've got my energy back again.
I have short spells like this but they dont stick around long. I bet it is b/c we are healing and drained. Im still on clear liquids so I think that may contribute to it too.