Could also be your supraspinatus, which you REALLY do not want to fuck with, as it is the single most important rotator cuff tendon in your shoulder. I find the supraspinatus bears quite a bit of the load with overhead presses. That is why I cannot do OH DB presses; my left supraspinatus is torn irreparably, so I cannot stabilize the DB. Only barbells work for me for OH presses as a result.