Many times when starting a new way of eating (Atkins or not), there's a period of feeling unwell, muscle aches, head aches, crabbiness, bad breath, bowel disturbances and more!
When I was in ketosis, I felt like crap for the first few days until I broke through and felt really great, less hunger, no obsessional food urges and had less aches and pains in general. Your experience may vary.
I'm setting my sights on getting under 200 pounds. I'll reevaluate after reaching ONEderland!