Hi, I am 15 female teenager and have recently been having fairly mild chest pain (right in the centre an inch or so above the top of where the ribs end about the size of a 50c coin). It comes and goes trhoughout the day when I am resting not excercising, should I be worried?

Resting, as in lying down or leaning back? That could be plain old heartburn at your esophagus - either gas trying to escape as a burp, or food burning at the bottom of your esophagus instead of emptying into your stomach, or stomach acid backing up into your esophagus. Pain on the left side under your heart is also part of the general term heartburn. That's trapped gas at the highest part of the stomach.

Sip liquids (water or watered down juice). Buy some antiacids like Tums and chew when you also drink enough liquid. Sit up. Avoid caffeine, spicy foods, carbonated drinks, and chocolate, and whatever else bothers you.
Answer back if that isn't working.

Thanks for the reply! =)
Resting as in not running around just relaxing etc. Oh, and I don't know if it is relevant but I have also had trouble breathing a few times after eating a lot, almost like asthma or an allergic reaction or something.
Btw, the pain isn't a 'burning' more like a pressure pain..

You could have a food allergy, you could have a different esophogeal problem from above such as a hiatal hernia... time to get it checked out.