I was going to ask the same as Sara, why can't you eat and drink? Is everything just coming straight back up?
Can you sip on icecubes (just make sure they aren't tongue stickingly cold though!) and get something like ready salted crisps to just let melt in your mouth to try and get some salts back in you. You could also put a little salt in the icecubes.
As said about, if you are dehydrated then that could be causing the headache or at least making it worse.
Once you can keep some fluid down then get on rehydration powders.
How long haven't you eaten or drank for and are you being sick/diarrhoeah as well?