If I read your first post, you did not have a specific moment/mechanism of injury that causes your shoulder issue. Also, you have been lifting for 3+ years - did the shoulder issue just now recently become noticeable? Do you recall anything happening that made you notice it or made the issue start occurring?
From the video you posted, photos, and descriptions you gave, here are my observations:
- You are positive for a sulcus sign, which mainly means you have some inferior shoulder capsule laxity
- Looks like there is some anterior shoulder laxity as well, especially based off of your video
- Self-diagnosed with rolled forward/kyphotic posture, which photos and video prove.
- Not sure if it is from the position and actions you are in during the photos/video, but you look very upper trap dominant and seem to be lacking mid/lower trap/rhomboid activation and scapular control.
- You shoulder is not "dislocating". What you are describing are excessive shoulder translations and subluxations. Might be semantics to point that out, but I feel it is important. If you have congenital laxity throughout your body, than your shoulder may have likely been like that and just now due to some activity you are doing (or not doing) are causing pain.
First and foremost, as another poster already said, go find a shoulder specialist and get an MRI to determine where the laxity is coming from. Is is a labral issue, capsular issue, etc? Secondly, STOP doing what you are doing in the video - don't "test it out", don't show it off to people, etc. You are only going to worsen the capsular issue if that is indeed the case.
Would you be able to post your current training routine? The more specific in terms of exercise selection the better. I would suggest to find somebody proficient in shoulder rehab to help guide you through some proper exercise selection as well, as you are in need of some good scapular control. Assuming this is a capsular laxity/congenital laxity issue and assuming what your workouts are like (based off of what you described and your photos), you should definitely focus on some lower trap/scapular control exercises, shoulder proprioceptive exercises (when ready to perform them), and thoracic mobility drills (likely an issue due to the rolled forward shoulders).