It depends on if the pain is in your joints, or muscles at the shoulder. I know that when I'm working my chest, I do the bench press and alternate in with dumbbell flyes, and I can really feel it in my outer chest... ...of course, mine is more of a stretching pain.
What does the pain feel like? You say "stress", but this could also be attributed to the load that you are lifting, and the muscles that are working. Try lowering your weight, and doing a warmup set before hitting the heavier weights. (NEVER stretch a cold muscle, however, do a warmup first!)
Another option is to lower the weight and do slower reps - this helps reduce the stress at the joint, while you can still exercise the muscle.