Looked up symptom of tightness left side of chest, majority say heart attack, went to er but they said i was fine. still feel tightness in chest, not when i'm laying down usually, what should i do next?

This is one symptom of asthma or bronchospasm. If you are otherwise well and breathing comfortably, please discuss whether a pulmonary function test is indicated. Reduce stress, stay well hydrated and watch for respiratory difficulty and cough.

At your age the more likely issue is located just to the left of and behind the heart, where your swallow tube joins the stomach. Backwash of stomach acid, which is aggravated by reclining after meals or caffeine and many foods can produce such symptoms. They call it heart burn.