Rules of engagement for getting control of your racing heart are:
No caffeine, not just coffee but iced tea, sodas that have any coloring in them and definately no energy drinks, if you are a member of the 420 club at your age that also has to stop, limit your sugar intake and no chocolate, no red wine, no products with electrolytes in them like gatorade, make sure that you stay hydrated and i mean with just plain water not vitamin waters because they have sugar in them..limit your stress levels if possible, make sure that you get a full nite of sleep each nite, no burning the candle at both ends as they say meaning going to bed late and getting up early and taking wayyy too much on like working, going to school, going out with your friends lots of nites, etc. I know this is a long list but these are all things that can cause your heart to race and/or become irregular......hope this helps a little anyway.....as far as the weird pains in other parts of your body could be a sciatic nerve thing especially if you work out, indulge in sports or do repetitive things at work that involve your back or legs....good luck....
Can you tell us how fast "race' is? Best if you try to bring yourself to a physical and mental resting state before measuring your HR. A number would help us understand what you are talking about.