First of all..linking all your symptoms to vit d def..isn't gonna work.. You hvto take everything in to the picture. Your symptoms suggest of easy fatiguability and headache..now as all of us knw headache can have hundred causes..get a Hemoglobin done.low HB can be a cause..get an eye checkup if your work involves straining eyes a lot.. Avoid high carb and fatty foods..take adequate intake of juices,protein, dal etc ..