I am not a Doctor, but this sounds like a rhomboid muscle strain. I had this happen to me a few years ago and it was not fun. Was in good shape when it happened too.
http://www.med.umich.edu/1libr/sma/sma_rhomboid_sma.htm
I got prescriptions for muscle relaxers and potent pain killers. Was back to normal in about a week. Good luck sir.