Why are my eyes so tired?

Most likely dry eyes: This is likely due to keratoconjunctivitus sicca or dry eye syndrome. You should try artificial tear lubricants three times a day. If no better you should see an ophthalmologist.

Many causes: Many things can make your eyes feel tired. Naturally excessive near work causes the eyes to feel tired and this would include reading and computer work. The type of lighting used for these activities is important also. Dry eyes, allergies, frequent use of preserved drops, incorrect prescriptions or uncorrected refractive errors are other causes. Other eye diseases also cause this.

Dry eyes?: Tired feeling eyes may be a sign of dry eyes. You can try otc artificial tears 4x / day as a test. If that helps, you should see an eye md to see why they are so dry and for definitive traatment. Your eyes should not be so dry at your age.