Heart disease doesn't run in my fam, norm wt, BMI of 21. Bp 100/60, labs good, many normal ekgs, normal xrays. Still get chest and back pain, anxiety?

Could be. Or could be from reflux or musculoskeletal source or respiratory symptoms (--why are you smoking up to 2 packs a day?). If your dr. Has ruled out heart or endocrine source for symptoms, then ask about these other options. Once serious and specific-treatment sources eliminated, then can relax if / when it shows up.
Alternative answers . You should look into reflux as a cause for chest pain. You doctor can help w that. Anxiety can also be a cause of chest pain but there is no specific test to show that.