Pain on left side of my chest when i breathe feels heavy and little sharp. ?

Likely muscular: Sharp pains in the chest at your age are almost always from irritated muscles and chest wall, ie... your ribs. You probably overdid some activity, lifting, carrying too heavy of a backpack, etc. That being the most common reason, though, if you feel dizzy, lightheaded, dull ache pain , short of breath, then check with a doctor to make sure not your heart or something like reflux