OK, thanks for the additional information. The short of it is that once a shoulder has undergone a dislocation it won't 'feel the pump' in the same way as the non-injured side. The brain with has some apprehension with the movements and it will not allow the muscles to work as fully as they did before until they are dead certain that there is no chance of reinjury. Now that can take years, not months. With potentially more movement available in the joint the balance on the rotator cuff needs to be better than ever and the general necessity is to strengthen the external rotators/ rhomboids, lower fibres of trapezius and lengthen the internal rotating mechanisms, including the PECs (especially minor). Also important will be cervical and thoracic mobilisation as without that things aren't going to stay lengthened.
Importantly on the external rotators it is the eccentric strength i.e. the strength controlling the arm as it returns to neutral from the fully externally rotated position. You need to has a therapist show you the progress of this from an elbow by the side position, eventually with arms out to the side like a laternal bumbell raise position. It is light weight first and then speed progression with control at that same weight before you up the weight, then again speed control with that weight before uping again. I would not suggest cortisone as a useful tool at this stage. It might just hide the symptoms you need to ensure you are not doing any further damage to the area. Mentally take on board this could take 18months to feel more normal and taking a more general body approach to your fitness and core connection e.g via body pump classes or even cross fit with light weight might be a way forward too..