Occasionally, whenever i lay down at night i feel a dull ache in my chest by my heart and it stings sometimes. is this a heart problem or disease?

No: Usually at your age the problem is acid from your stomach going up your esophagus. It is called GERD or acid reflux or heartburn. It can be a dull pain or even a sharp pain but watch what you eat or drink before lying down The acid can hurt your esophagus over a period of time. There are medications over the counter or prescribed which can help Check with your provider