The best thing to do is to err on the side of caution and go to a doctor and be evaluated. Several things came to mind as I read your description. First, you said it is a sharp pain. AS A RULE, which means not every single time, sharp pain in not an indication of cardiac condition. Having said that, I have to say it is still at least possible it is. You need to be evaluated while it is happening. An EKG is sort of like a photo; it takes a "picture" of what is happening at the time. If you wait until after the pain is gone, then an EKG can't take a picture of what's happening because it's gone. An EKG takes the equivalent of an electrical "photo." That's one thing: it probably isn't cardiac, but you need an EKG while it's happening to be sure. If It's sharp, it could be gas, it could be gall bladder and it could be pleuritic, or having to do with the lining around the lungs. It could also be from within the lungs. You are a bit young for gall bladder problems, but it is not outside the realm of possibilities, especially since you say it comes on after eating greasy foods. The fact that it gets so bad you can't lie on your left side also says to me gall bladder. It could be a chest wall spasm, or diaphram spasm or really any muscle could go into spasm. You know how you get charlie horses in your legs if you don't stretch properly, well your chest or lung musces can also go into spasms and "cramps," especiallly if you're a runner. There could be a tiny little air bubble between the lining of your lung and your actual lung. You could have a stress-fractured rib. Not likely, but possible. All these things can cause a lot of pain in the area you described. You need to go have diagnostic tests to find out for sure what's happening to you. Don't put it off. It's probably not serious, but until we know that for sure, better to be safe than sorry. Tell you parents and tell them you need to get to the E R the next time it happens so you can have an EKG at the time of the pain. And good luck with this. And don't wait until it happens again to tell your parents that this has been going on. You can also call your doctor and say what has been happening.