OMG ! I apparently have a problem and didn't even know it. Comparing you to me chest-wise, I don't think you have a problem. Mine is much worse. Nobody complained about it when they hacked it open for bypass surgery, and I had never thought of it as a problem.
That being said, if you were of the female persuasion, THEN I'd say you got a definite problem.
I'm certainly not a doc either, but I also have pectus excavatum, and your's doesn't look bad compared to mine... Mine is more of a deeper cup shape in my sternum... The doctors I've asked have not been concerned, I would'nt worry about it unless you are self conscious, but your's isnt bad at all so I wouldnt be. Ask your doctor the next time you have an appt.
It's kinda hard to tell from a picture, truthfully. You don't say how old you are, but I think that once you go through puberty it is not likely to worsen. One of my boys has a pectus that looked like yours but has never caused him a problem. In fact, he was a D1 distance swimmer. Just ask your doctor what s/he thinks. What we think doesn't really matter!
I am not a doctor so I didn't check out the picture (I wouldn't know good from bad..lol). Has your doctor said anything about the pectus excavatum? I was told, in my early 20's, that I have pectus excavatum, and so far (I'm 50) it has not been a problem. For what it's worth, I think it is often associated with a straight back. Good luck