It is very normal to feel sick in the beginning. Your body is going into a kind of carb withdrawal. If you keep eating carbs thinking that will make you feel better, you are just going to repeat the cycle. You just have to stick with it and get through the sickness stage. It should only last a couple of days and then you will feel much better. When I first started and then again after lots of carbs over the Christmas holidays, I felt very sick, actually even threw up, but it's worth it to suffer through it.