Spine / Back of the U

Most recently my ability to feel or perceive what I've thought of as the back of the U has travelled futher up the back. I thought that the back of the U was from the lower part of the ribs down towards the sacrum but now it seems like the stretch in my back can be felt slightly higher than the bottom of the ribs. When I was standing earlier in the day and I was feeling more of the tissue/stretch it almost felt a little like spine lengthened. Then later when I was doing it in the evening I was noticing that it seems like the higher up part of the stretch was more on the left side. I know I have a bend in the spine towards the right in my lower back, I wonder if the stretch is trying to pull or straighten out the spine. 

I also have not had a lot of clarity on the front of the U but it seemed like this higher up stretch that I was feeling maybe made the front of the U a little more clear, although I'm not sure if I was feeling it or maybe just imagining it. I've been trying to work on feeling the pushing of the shoulder but have not had much more clarity in that region yet but I'm wondering if the feeling of the stretch in the spine maybe is leading towards more awareness in the transverse stretch in the upper back.

Standing FBD