Arthritis in shoulder or torn rotator cuff.?

I have been lifting weights for 2 years. Lately, my upper arm appears to have swollen. It looks like muscle tissue. It has become painful to move my arm behind my back etc. How do I know if this is a torn rotator cuff from excessive lifting or arthritis? If it is arthritis what is the procedure to remedy?Is it also ok to contiue lifting weights? If it is torn rotator cuff, is there more damage if I wait 8 to 10 months for the operation, since I now am working overseas? thanks