As a judo coach/player for over 40 years now, I have had operations on both shoulders with the same issue you have. Most the time cortisone injections do help but only for a few weeks of pain relief as its only the inflammation that it is treating. As someone has mentioned a good Physio is a better option. They will prescribe a range of exercises to help build the supporting muscles to make the area stronger and improve your range of movement. However if your rotator cuff muscle is torn it will need repairing. It could also be an impingement issue, I.e. Calcification build up on your bones that are hitting the underneath of your shoulder blade, or tearing in to your muscle. Either way you ideally need an mri scan, that's the only way really to know for sure what the problem is, your money would be better spent getting an mri as you could throw a lot of money at Physio, injections etc that may be pointless. My shoulders are good again now as the surgery for these problems is fairly routine and although painful post surgery, they only take around 6 weeks before you get back to normality. I noticed the pain originally when I found it painful washing my hair, I.e. Lifting my arms above shoulder height.