Headaches.....

You should probablly see a doctor about it. I had bad headaches that would sometimes cause me to blackout and so when I went to the doctor and got a cat scan I found out I had a brain tumor. It's better safe than sorry but not eating can definently cause bad headaches too and nausea.

You ask if not eating can cause headaches which makes me think you could be skipping meals. It maybe if you are doing that that you could be dehydrated as a lot of our fluid that we need each day we actually get from our food. If you cannot be persuaded to eat regularly then at least drink lots of water each day and take a multi vitamin. Stress can cause headaches but it also causes other symptons such as bad temper and loss of sleep. Try taking a bit of time each day to relax or take a herbal supplement such as Kalms.