Im 17 and have pain in my upper arm and i have a anxiety disorder. is this probably a heart attack or just stress/anxiety?

Unlikely cardiac: It would be exceedingly rare for a 17 year old to have a heart attack without a predisposing condition. However, if you are having excessive caffeine or are a cocaine addict, or are taking amphetamines, this can predispose to a heart attack through overworking the heart. If your symptoms persist, see a doctor in person to get checked out so that you can put your mind at rest.