The good news is that it's probably not your heart. Considering how wonderfully active you are, it may be a pulled muscle or some irritated nerve. The best way to find out is to see your doctor. See what's going on, make sure everything is OK then go for the tryouts. Good luck with those. It can be a lot of fun. My daughter did cheerleading for awhile and it's quite strenuous.
I agree! See your doctor if you want to be reassured. Chances of you having a a form of heart disease that would cause 'true heart related chest pain' is basically nil in your case. If you had that, you would NEVER be able to do the activities that you are doing. And for you to have adult related chest pain from blocked arteries, forget that one too; it takes 20+ years to develop that type of chest pain. Go have fun!