Hi Skyler,
My 15yo son has had this pain for a couple of weeks now and was checked out.......his heart was fine and it was attributed to costochondritis which is basically what the last post was indicating (an irritation or inflammation of the cartilage in your ribs). He has reduced any activity (such as situps and such) and is taking an anti-inflammatory (Motrin). I hope you feel better soon. I am not a doctor so I cannot diagnose you, but I did want to let you know that my son had something similar.
These pains are not uncommon for your age group. You are most likely experiencing a growth spurt that puts quite a bit of stress upon your intercostal spaces (this is the cartilege in between your ribs). When it is pulled, it causes stabbing, almost angina-like pain. I am not an MD, so, if this does not subside soon, please see a doctor. My son experienced something similar when he was your age and it didn't last more than about 10 days.
Stabbing pains are not indicative of heart disease. At your age, i don't think you have too much to worry about, certainly not based on what you have written on here.