Shoulder injury

I went to a doctor last year because i have shoulder pain. He put me on 3 months of rehab which stregthened my shoulder, however throwing again this year, I feel the pain once again. I can play catch and throw about 75% speed without any pain whatsoever, but as soon as I snap down hard and throw, I feel burning in my shoulder. The pain is a 9 on a 1-10 scale. Any thoughts on this?