Please post about 2 days' worth of menus, so the community can troubleshoot your problem. Without knowing exactly what and how much you're eating, we're flying blind.

Taking a shot in the dark anyway, you might be low or out of balance on electrolyte minerals (the ones that make your body's electrical functions work): calcium, magnesium, potassium, sodium. The early stages of a LC diet are extremely dehydrating, and minerals leave with the water. Dr. Mike Eades wrote an informative post about counteracting this effect.

Also, read through the these threads and see if any advice fits your situation:

• Advice for the Newbies
• Low-Carb Newbie Basics! Check Here First!