What Causes Numbness In Fingers With Pain In Shoulder And Neck?

For the past 2 months my #3 and #4 fingers in my left hand have been numb. I have also been under some stress and I also have been having I think it is pain with my sciatic nerve and pain in my kneck and shoulders. What are the causes for the numbness and how can I relieve it along with the pain in my shoulders and kneck.