I hurt my back... help!!!

[Desiree]

Well after slacking up for about 3 weeks since my car died and not having reliable transportation to and from the gym, I was all geared up and ready to go back starting today. This morning, I did my normal morning routine then as I reached for the back of a chair to sit down, my back started to hurt immensely. It was like a knife was stuck in the right middle of my back (near my lungs) and I felt like I couldn't breathe or catch my breath. I screamed for DH and he helped me get upright. He suggested to try to stretch a bit then lay down. After a while it did ease up but now it is really sore and achy. I took some Advil to try to help. Anyone know what this is? Did I pull a muscle?

I am able to tolerate it but it is uncomfortable.