Shooting pain from behind my ear down my neck and into my left arm. no chest pain. i'm 21 and active. could this be heart related?

No: Given your age it is very unlikely to be caused b ya heart problem.

Unlikely: Not likely to be a heart problem. Could be pulled muscle, strain, herniated disc or other such problem. See a doctor and get this checked. Go to ER right away if pain is severe or you develop shortness of breath, vomiting, excessive sweating or other changes. Good luck!