What is wrong when you have shoulder pain and numbness?

Check neck. Symptoms could be from the shoulder or referred. Common referred sources include: abdomen, heart and neck. Shoulder sources include: arthritis, labral tears, instability, tendinitis, rotator cuff tears, bursitis, painful bony spurs etc. Shoulder blade pain can be from the neck or bursitis around the blade. A herniated disk in the neck could be causing your symptoms. See an orthopedist.
Depends. A problem with the shoulder can cause both pain and sometimes numbness. A problem with the neck can do the same thing. It is impossible to tell what is wrong without a physical examination and this should be done by a doctor.