Having heart palpitations and tightness in left side of chest. what could this be?

Likely Anxiety : At your age, i'd consider it as anxiety. Unless you are at high risk of suffering from heart attack. Family history of sudden deaths from heart disease, obesity, cholesterol problems, diabetes, hypertension, kidney diseases can all increase the likelihood of heart disease even in young people like you...Being physically active and healthy food habits are to be followed on a regular basis.