I work with semi prof rugby and at 6 months we have them back playing and 18 weeks they are all in the gym doing strengthening. At 18 weeks and if the surgeon hasnt booked you to see him back, he is confident in his repair and this is the time to go back to the gym. The accelerated program is designed with modern repair techniques in mind and safely guides you through recovery. Its important that you regain strength around the shoulder now before pre season so that is protect the repair. Pains around the shoulder are not neccesarily a bad sign, it may just be as you have worked muscles that havent been worked, it may be because some muscles are overworkign to compensate. I would go back to see the physio and ease off the exercises with the elastic until it settles, maybe use a longer band or twist out with you elbow more into the side.