Am I having back spasms, or did I pull a muscle in my back?

I was playing basketball, and right when I jump up for the lay-up I feel something in my upper middle back either pull or start to spasm. I have never felt pain like this in my back before and I consider myself to be above average when dealing with athletics. At first it was hard to even walk around, hard to breathe as well. It feels like there are two tightened up on the right and left of my spine. The hardest thing for me to do is sit-up. Sitting up puts the most stress on those two spots. I'm not sure if these are spasms or I pulled a muscle? If you can help me find out what it is and what the best way of going about it is that would be great. Thanks.