As Pandora and Karen have already said - stick at it. Most people are in full ketosis and feeling fine after a few days, so you should be fine soon, and certainly by your first weigh in.
Some people cut down on their intake prior to starting and this eases the feelings of ickiness as the body has already started to adjust. If you did not do that and went straight in at the deep end ....
Just stick at it - you are almost at the top of the wall. A couple more days and you will be at the top, and believe me - the view is brilliant once you are there!
Steve