Hi happychic, it's different for everyone although I tend to get a burst of energy after day 3 or so. I also found some weeks I lacked energy more than others. Maybe you could have a check up with your doctor to check blood pressure etc if you're still not feeling great. In my experience, most doctors are really happy that people take their weight loss management into their own hands. Keep us posted on how you're getting on.
Happychic, it's normal, so don't worry. Days 5 and 6 were my most difficult days. Just stick with it , it's worth it and by Day 7, or hopefully Day 6 for you- you'll feel great.