I've had pain in the muscle of left shoulder blade for one a year now. it comes and goes but sometimes is so bad i can't function normally. sometime?

Most likely it is : Muscle tension, poor posture &/or deconditioning of upper body & core muscles. Deep tissue massage by a professional can help. Pt may also be of great benefit for heat, ultrasound, massage & learning exercises that will help. Of course, given age & gender, prob warrants making sure heart is ok, especially if you have any risk factors for heart disease, although pain doesn't sound typical.