Did you have any imaging done, most notibly an MRI?
If not, you may want to since this is a lingering issue.
However, in my experience, shoulder ailments take a long time to clear up.
Careful with any stretching, it's already a lax joint, especially with an injury. I've noticed strengthening and stability work to be most helpful for me in my recovery. With stretching, most issues come from tight pecs and lats, so give them some love. That'll free up the joint without stretching it directly. I like to roll out the areas with a med ball, and stretch them laying over a med ball on upper back, with wide grip on pvc, arms locked out over head. Lay there for 2 mins.
Take your time with this. Rushing will get you in trouble. 800mgs Vitamin I 3-4 times per day for a week may assist you. I'm not a Dr though