The PT will not be able to diagnose RC tears with an ultrasound. Mild but chronic shoulder pain could be caused by lots of things, and you didn't say if it was one or both shoulders. If safety is your primary concern, and you are training for physique and are happy with your current strength and muscle mass, I suggest you stop benching and pressing immediately, and just do some maintenance on machines every couple of weeks, after this pain subsides. Dumbbells can be dangerous.