Could the ER be wrong about diagnosing a heart attack? They did a blood work up, ekg, & chest xray on me. Still don't feel right.

Possible. But extremely unlikely. 18 year old females very very rarely ever have heart attacks. And er's are very good at making sure that patients do not have life threatening illness before discharge. It is much more likely that you have another cause for your symptoms. You should probably see your regular physician to explore those non life threatening causes.
It depends. Generally, if you had 2 normal blood tests (tropomin)several hours apart, you did not have a heart attack. It would be extremely unlikely, but not impossible, to have a heart attack at your age.

Related Questions

I am 18 years old female. Normal heart echo (twice) ekg (many times) chest X-ray blood work and physical examination by cardiologist. Can I have cad?

Hard to say. We do not know the reason you had all those tests done, whether they were interpreted correctly, and what your history and exam findings are. Without all the available information it is hard to guess what your status is.
18 yr old, CAD? No. It would be VERY unlikely that you have the atherosclerosis build-up in your arteries that causes blocked arteries (CAD) at only 18 yrs old! I wonder what symptoms you keep having that have prompted all that specialised testing? See an internist who can help you understand your symptoms. Best thing to avoid CAD is 1) don't smoke, 2) eat a healthy diet (vegan/vegetarian), 3) exercise regularly.