For the past 3 weeks my eyes have been watery, itchy, and red. How can I soothe them?

Itchy eyes. You may be suffering from allergic conjunctivitis. Try some cold compresses and zaditor (ketotifen) twice a day for 3 weeks. If you have no relief after this time, call your local ophthalmologist.
See an eye doctor. This most likely represents allergic conjunctivitis. First, determine if you have been using new detergents or fabric softeners. Any new pets? Did you move to a new locale? If over-the-counter allergy eye drops or artificial tears do not relieve you in a day or two, you should see an eye doctor.