It's both. If I have a shirt on I become hyper aware of my shirt touching my collarbone. If I'm not wearing a shirt I'm aware that it exists. When I'm not wearing a shirt it's like I feel how my skin stretches from my neck to my shoulder, or how my skin folds between my chin and my collarbone.

That could be a possibility, I do have dry skin.

Yeah everything you described is exactly how it is for me. I even held shirt collars in my mouth as a kid too.