Congratulations on your square overspilt, that’s awesome , and good luck on your back! I can totally understand the frustration with your back, I feel the same about my upper back and shoulders! But once I started working on it, my back and I became friends ;), and now I actually like training my back, it just takes time and patience. Yesterday I tried to rush my back stretching routine and I couldn’t do too much without my shoulder locking up. So my best advice, is breath deep and take your time.