If the doctor says your eyes are OK, try the following:

Wear a hat. The sun will do a number on a bare head.

Make sure you drink plenty of water.

Use UV protected sunglasses. DO NOT GET CHEAP ONES, they will cause more problems than they help. If you want a SOLID color, look at some Gargoyles. Rayban PHOTO REACTIVE are also good (they get darker in direct proportion to the amount of UV you are exposed to).

But first and foremost get your eyes checked (and a physical is also a good idea). The eye and headache MAY be symptoms of something else.