I'm not sure about braces, but there are many hidden sources of metals. You may have tainted tap water and many other possibilities.
I've heard some people who discuss the possibility that they are suffering from aluminum toxicity. I'm not sure about that though.
I presume that you don't have silver fillings. I also presume that your symptoms developed after you got your braces.
If you would like to try chelating, and you are not sure which metal may be causing your problems, I would suggest DMSA as part of the Cutler protocol since it works with some of the most common metals, including lead and mercury.
Do your research first and make sure you know how to chelate and that you are sure chelating is what you want to do. Chelating is not completely without risks, no matter what method you choose.