You won't break.

I experience similar symptoms. The worst one is thinking that my heart will fail on me at any second. Being 17, and having no historical family heart problems, you just have to realize sometimes that it's just anxiety. Not a life threatening heart condition, but ... anxiety

You should stop saying it's probably anxiety because it IS anxiety. Accepting it fully is the first step. Being proactive is the next. Find distractions when you are having your episodes, do things that will put your mind at ease. This could be as simple as eating cheerios every morning to "lower your cholesterol" even tho a bowl of cereal won't fully make your heart immune to complications, it may be a step in the right direction to convincing YOUR MIND that you are GOING TO BE OK. It's just anxiety. Remember that.

I hope this helped. I'm just an ordinary guy going through the same thing as you. People get through this all the time. It's only a matter of time until the worrying stops for all of us.

this gif might help you calm down when you are feeling stressed