For The Last Few Weeks I Have Been Suffering A

For the last few weeks I have been suffering a dull ache down my right arm. This has caused pain sleeping at night. I can raise my arm above my head but painfully and not as far as the left arm. My history is as a Self Employed book seller for 10 years, attending fairs every week and lifting heavy boxes with books. This finished in 2006 and wonder if this could be the cause now?