What is a good skin care regimen for high amounts of sun exposure?

I teach tennis six hours a day everyday except Sunday. I apply sunscreen before I go out (spf 30 or 50) and I wear a hat or visor. I am still getting sunburned on my neck and shoulders and my skin feels like it is not taking all of this sun so well. What can I add to make a good skin care regimen that fully protects my skin and prevents further damage? I am 23 with combination skin.