I'm 17 and sometimes I get a slight straining feeling around my heart. First couple of times I thought it was because my bra was too tight but it happens when I'm not wearing a bra either. I do quite a lot of exercise but my diet isn't too good. The pain happens a few times a week maybe. Should I go and get it checked out?
I would go to your GP to get professional advice on it, they may listen to your heart and go an ECG which will monitor the heart rhythm, none of this is at all scary, but its worth going if the pain is worrying you.
It could be that the muscles around your chest are strained due to the exercise you do.