It is always important to rule out the things that kill people, namely cardiac causes of chest pain-- which would be uncommon in a 28-y-o person but not impossible. EKG, enzymes, etc cannot rule OUT cardiac causes, as they would only be abnormal if you had a heart attack-- and may not show anything if you were having angina. But again, such a diagnosis is unlikely-- but a stress test would be more evidence to that effect.
The doctors are working against each other a bit; one gave you nexium, which would reduce gastric acidity and promote healing of an irritated esophagus or a gastric ulcer; the other gave you aleve, which will irritate the stomach and esophagus. It sounds like the aleve was to treat 'costochondritis', inflammation of the junction of ribs and sternum that can flare up after exercise or even after stress.
I recommend staying on the nexium, and if you use aleve, use it only on a full stomach. You might consider taking antacids when you have the pain; if that relieves the pain quickly, that suggests that stomach acid is the culprit.
Also I am 28, Male w/ no serious medical history and generally healthy. Since late November, I have lost considerable weight because I watch my diet now and walk a lot. This experience also led me to quit smoking, drinking coffee/alcohol, and to lead a more healthy lifestyle. In other words, lifestyle changes have not expedited the healing process.