Hey, a little update. I have been doing the eccentric pec minor exercises, and I actually got the pec minor sore, I can palpate it and feel the soreness, but that's definitely not the part that hurts. For whatever reason, I can not find any part that is sore to touch.
What's strange is that I can feel the pain during passive scapular depression. Like I sit in my computer chair, which has armrests, and with my elbow on the armrest, my shoulder is elevated. When I sit up straight, I can feel pain just from the shoulder dropping, but the pain is, oddly enough, right underneath my pec. This again seems like pec minor right? During a passive depression pec minor still contracts slightly since it gets "tugged"?
I also noticed that when I am "hunched over," in spinal flexion, and actively depress my shoulders, it doesn't hurt. But when I stand up straight and push my chest out it hurts a little just to stand like that, and the pain increases if I actively depress the shoulder. This also seems like pec minor I think, since pushing my chest out pulls the scapula down and back, loading pec minor.
Maybe it's just some weird pull so I can't feel the pain, or maybe it's some sort of injury near the attachment point itself, maybe the costal cartilage or something?
It is beginning to hurt less, so hopefully I can begin planche training again soon.