I'm 20 i smoke pack a day eat well exercise this morning i had left chest pain made me light headed and throw up very weak is it from my anxiety or?

Very likely: You feel guilty about your smoking and sounds like you have a history of anxiety which can lead to lightheadedness, nausea and chest pain. Rather than worrying about your health, do something positive about it! quit smoking asap!

Quit smoking !: Since you are a 20 year old woman, i think anxiety is more likely than heart attack, but you should definitely quit smoking, and see your doctor.