How long do you stick at it? A lot of people get bad headaches in the first few days of SS. A good way to reduce this/stop it is to reduce your carb intake for a week beforehand. You will find that you will slip into ketosis a lot easier & not have the side effects associated with carb withdrawal on the first week of SS.
Good luck, it is worth getting over this hurdle & getting into the easy part of SS'ing.
Nicky