Today I began to workout in my garage and decided to start off with a 110# behind-the-neck jerk (My PR is considerably higher). However, as the weight was halfway up, I realized it wasn't gonna move any further. I felt something odd (not really PAIN then) in my back, then went on to try jerk from the front rack position, then a front squat, then a back squat. As I came up from the back squat, I realized that everything felt uncomfortable (and I was tired) so I racked the weight and went inside. Now, 30+ minutes later, I have this dull (but fairly painful) ache/pain in my upper back, about even between my shoulder blades. The pain is exacerbated when I take a deep breath, so it's somewhat shallow right now. What just happened? What to do? Thanks to any responses.