Its most likely Stress
or something of that sort. Its really not that common for a child to get heart disease
unless you were 1.born with it 2. eat really unhealthy and dont exercise 3. are over weight and things like that. Heart pain and palpitations are scary, but yours probably do not mean you have heart problems(be thankful for that! its not fun having heart problems) But if it is really worrying you, ask your mom to schedule you a doctors appointment.