Thank you for the query.
Headaches after skipping a meal is most likely caused by low blood sugar
level. Other symptoms like nervousness
, sweating, shaking can also appear. You can easily check it by measuring your blood sugar level next time such headache will appear.
Your nausea after some meals can be caused by acid reflux disease or peptic ulcers. Food allergy
is also possible. I suggest you to visit your doctor and consider upper GI endoscopy and allergy tests
Hope this will help.