I am 16 never smoke and cant stand caffine and i get something very similar. I just recently had to go the hospital because of my heart, it beats to fast or somehing, and i had an ECG, chest x ray. They all came back fine but because there is a heart problem in the family and im suffering from dizziness, tightness of chest, odd sensations in the heart, they are doing more.
From my experience, i can advise you to yes relax and take you mind off it When you do have a sympton or odd experience, write them down along with what you are doing. If the problem gets worse, and you have more things wrong, i would suggest you see your doctor, let him/her know when you get them, how long they last for etc and say how it effects you. They should do something about it, eg. more tests, keeping an eye on you.
Hope that helps. xx