Meows...what were your blood sugars running before you started low carbing? The reason that I'm asking is that if your body was accustomed to a higher blood sugar, even though it was damaging your body, you can actually feel like your blood sugars are too low when they really aren't once they start getting closer to the normal range again and can produce a lot of the symptoms that you were reporting. Combine that with eating a lot of frankenfoods and not enough calories and I'm not surprised you were feeling like something the cat dragged in and then dragged back out again!
I agree with everyone else...ditch the bars, shakes, etc...(things we refer to as frankenfoods because they're so highly processed) and eat whole unprocessed foods for a few weeks. I'd be willing to bet you won't believe the difference in how you feel.