hello, last night around 7 pm I had dosed off and got woke up by a severe pain behind my left should blade ( lower left ) and I thought maybe I was laying on it wrong but got woke up around 1am again with this pain , went to the ER and they did an EKG and I was sent back to the waiting room due to there were 13 people ahead of me I sat there for 2,5 hours and left and came home, I figured the EKG must have been normal , anyway what could this be?