I have not been here long enough to have observed any of your previous posts. You have a good attitude, and hopefully you will post here for a long time.
Irregular heartbeats can be caused by eating the wrong kinds of foods. Allergies do this to me. And yes, asthma can make you feel miserable.
Even a bad cough can dislocate a rib or two, and cause chest pains. That I have had too, especially when I had pneumonia. It went away with rest and the help of a good chiropractor.
Do you have a health clinic at your school? At our school, visits are free. Lab testing may cost a little.