have you seen a doctor about this yet? where are your parents are they where you can talk to them? your very young and you need to address these problems before they become a part of your life and you get to where your home bound. sounds to me like anxiety but you need to be checked out by a dr.
The first issue is are you already diagnosed with heart disease or do you have another issue? Really without knowing where you are leaves numerous possibilities. Write down all symptoms and get to a Doctor. Rule 1. if the Doctor you choose is too lazy to find the answers replace him with another Doctor. Rule 2. Travel, if you are really sick, and you know when you are really sick or not, don't ever be afraid to travel to a major medical facility, medical college and seek out medical help if your insurance allows it.