You can't be sure it's a tear until the doctor checks it out. For years I have had a lot of extreme shoulder pain (yeah, I'm working on my seventh decade of life) due to overuse which causes swelling in the shoulder joint. A shot of steroids fixes this up within hours. If this is the case, learning a new paddling technique may surprise you as to how well you feel at the end of the day.
When I started kayaking I thought this wasn't going to work until I learned how to paddle like they do in ocean kayaks. It took awhile to for it to feel natural, but now I no longer have shoulder problems even after padding all day. It takes some practice for it to feel natural, but before you know it you'll never go back to using your arms only.
Check it out, it may help you out. The tutorial is a animated video step by step.
Paddling Basics.
http://kayakpaddling.net/