Thanks for writing your query.
It will be helpful if you give more information on :-
1. Your age.
2. Your job profile.
3. Any medicine you are taking.
Your symptoms, including headache, can be due to low blood sugar
You should get yourself clinically examined by your doctor.
Following investigations will be helpful :-
1. Blood sugar level (Fasting and PP).
5. Serum electrolytes.
Also monitor you blood presure.
Treatment can be planned according to the reports of the above mentioned investigations.
Eat lots of fresh fruits and vegetables. You can drink Oral Rehydrating Fluids, if you are feeling dehydrated.
I hope this is helpful to you.