Hi Sarah,
Welcome to the forum.
Some people don't get a headache others do, mine was like a caffeine withdrawal headache, but it wasn't too bad.
My best piece of advice to a LL starter would be to stick to abstinence 100%, do not waiver.
It is so much easier to stay safely on packs than it is to eat, even a small amount.
Make sure you drink the water it is very important.
Look forward to your posts.
Good luck on your new journey.