Whenever I wear a backpack (even a light one) the area just above my collarbone hurts and my right hand goes numb. What could be causing this?

You may be describing symptoms of a problem called Thoracic Outlet Syndrome (TOS). The major blood vessels and nerves to the arm and hand travel from the neck under the collarbone and down the arm.

Anything that changes the normal anatomy in the neck, shoulder, or upper chest areas can put pressure on these structures. Sometimes there is an extra (cervical) rib contributing to this problem. In other cases fibrous bands of tissue interfere with the nerves' movement and ability to slide and glide in their coverings called nerve sheaths.

If these symptoms persist you may want to see a doctor or physical therapist. Sometimes posture or muscle weakness can cause these symptoms. An exercise program may be all you need. In other cases, surgery may be the best approach.