I wanted to know why it feels like my heart itches?

Probably not heart: This is an unusual symptom for heart disease and in the absence of other symptoms I would see your primary doctor to rule out, for example, a skin disorder. If your are experiencing something different, such as pain taking a deep breath, that is a potentially more serious problem (like pericarditis). At your age, this symptom alone does not suggest a heart problem.

Chest wall itch: You are young to have undetected heart disease. Heart itch can sometimes be associated with palpitations (extra heart beats). As long as you run, jump and play like others I would not worry. The itch is most likely coming from the skin on your chest wall. If you have other symptoms like chest pain, shortness of breath or cyanosis (fingers and lips turn blue) I would see my doctor.