Pain under left breast and chest

So, for as long as I can remember I've been getting this sharp pain under my left breast and towards the center of my chest. It's more intense there but I get some pain on my upper chest too. It hurts even more if I take deep breaths. I'm 19 now, and I get this pain only occasionally, say once every number of months, but sometimes it's more frequent. It usually goes away after a minute or so, but this time it's lasted for over an hour.

I've found it hurts worse if I touch it, bend down in any direction, or lie on my side... or front... there really isn't a comfortable position, but it hurts less if I lie on my back. It scares me a little because the pain is so close to my heart, and there is a history of heart disease in my family. I've also considered it to be my lung, but I don't see how that could be possible as my lungs have never given me any trouble.

Anyone know what it is? Any help is appreciated.