Why Am I Getting Pain In Neck, Shoulder And Back?

I am Murali from Andhra pradesh, India. I am working as Data entry operator in Tanzania. I am sitting before the computer 10 hours max daily for work. From the past 30 days I am suffering from neck pain which will travel from back to fore head. Some time I will get huge weakness in my knee joints. Some times my shoulders will paining. I got blood pressure in the month of March'12. Physian prescribed Olmax-h.