Sitting at a computer can put a lot of strain on your body without your realizing it. The average person only blinks about 15 times a minute when looking at a computer screen, and that is less than half of what they should. The less we blink, the less moisture is delivered to our eyes which will make them strained and sore.

Make sure you are working in a well lighted area and aren't just using your monitor as your only source of light. Take a break from your computer every so often to allow your eyes to relax with some more natural light.

Since you are sitting for long periods and not moving, I'm sure your muscles are a little lacking on oxygen. The muscles rely on movement for circulation and oxygen and are also a main part of the reason why blood can make it back up your legs back to your heart.

So again, while you are taking a break from your eyes, take a gander about the room or step out for some fresh clean air and walk around.

I think the tingling sensation in your head will go away if you do this. The reason why you are tired at night is because you are sitting all day. Not doing enough can make us feel tired too. Get outside a little more, take a walk, and get some air.