a heart attack, or a case of hypochondria?

Am I having a heart attack, or a case of hypochondria? I've had this persisting 'knot like' pain in my left shoulder blade for a few days, which has steadily gotten worse. The back of my neck keeps getting tighter and radiates up my head. From shoulder to shoulder, my back has consistently felt tighter and tighter. I'm a little dizzy tonight; I've noticed I ran into one of my walls twice and tried to put something on the counter using my peripheral vision and missed it completely. I'm coherent though; I know what day it is, the time, my name, etc. What really concerns me is this cold feeling I'm getting in my left arm; it feels as if I'm being injected with cold saline through an IV because it will flood my arm in a wave and then dissipate. The cold returns though, in waves, and my left hand feels tight, harder to move, not as limber as my right.
Due to money issues, running to the ER isn't quite up my alley unless I'm pretty sure it's a heart attack. I've had chest pain before, and was told it was inflammation of the stuff between the ribs because my EKG had come back negative. However, this feels quite a bit different than that stabbing pain. What should I do?