Rudy, check out these links, and do some searches yourself if you want.
Pectus carinatum is what you want to research on those pages. I'm not a doctor and it's hard to tell what you have based on pictures alone, but this would be my guess. I myself have/had pectus excavatum which is the opposite of what you have. I actually got operated on much younger than most will because mine was pretty bad. My dad tells me I use to be a whiney kid, then after the operation I told everyone my chest didn't hurt anymore. No one even knew that my chest hurt to begin with.
With both pectus carinatum and pectus excavatum things usually develop or worsen around periods of growth, quite often more so around the time of puberty. This is actually about the best time to deal with it as well according to everything I have read.
I'm quite surprised that no doctors have said anything to you besides "you're fine". If pectus carinatum is what you are dealing with, to a certain extent the doctors would be correct, you are fine. Many people go on living long, pretty much normal lives with either deformity. One of the worse side affects for most people is psychological. But this condition can indeed cause pain or discomfort and also prevent full use of your lungs causing you to feel you dont have much stamina for strenuous excercise.
I would read about it, think about it, talk with your parents about it and see what they think. Like everyone else has said, there's no need to panic or worry though.
Again I'll state that I'm not a doctor and this could be something entirely different, but it's what it looks and sounds like to me. I would discuss it with your parents and have them or yourself talk to the doctors you have seen in the past and at least get some info from them besides "you're fine..."
Like I said already if this is what you have it is something that you can live a normal life with, but it is treatable. I'm not sure how much that sort of thing costs though. If your family has insurance I'd make sure that your parents make it clear to them that you do have pain and any other issues that this might cause so that someone might take it seriously. For the most part insurance will not cover cosmetic surgeries and this would be considered one unless you could prove otherwise.
Good luck, relax, and don't give up.