well instead of putting on a loose shirt i suggest you get to the root of the problem, the shirt IMO will only provide a temporary relief, if you dont address the problem with you shoulders right now they will come back later and possibly worse. my advice is to take it easy on you bench workouts, still train but stay away from movements that hurt your shoulder. do alot of shoulder work right now, internal, external rotations, general delt exercises, anything you can do to tighten up and strengthen the area. also make sure your form is perfect, this can be the cuase of your aching shoulder. also if you squat take your hands out as wide as you can, it will take some stress off the shoulders.