Well I'm not sure what they told you to eat for your pre-conditioning, but what my counselor told me went in one ear and out the other. I mean, I've been through so many diets and programs that I knew that this was my last week before 'slavery' so I used the week to get all my cravings out of me, and gained 2 lbs as a result.
Now I'm not saying to do that, but I don't think you should suffer, and I think you can probably relax a bit since you aren't technically on the program yet. Do you have something light you can eat? Like maybe a slice of toast, wheat, with a tiny bit of peanutbutter. Or maybe there is something in your fridge that you won't be able to have once you start, like yogurt?
The headaches are probably due to caffeine withdrawal, I think some people say to not cut out caffeine cold turkey but to make it gradual, by mixing half regular coffee and half decaf.