I have what is probably the same (or a similar) condition: Amelio-genesis Imperfecta. Basically, when my adult teeth grew in, they grew with malformed, super-weak enamel. After a couple years, all the enamel was rubbed off, and my teeth began to deteriorate. I got veneers, which still didn't help because a strong bite popped them off in my sleep. Too expensive to replace, so I've been stuck with my gradually wearing-down teeth since then. Last time I talked to a dentist about things that could be done, the recommendation was for a full mouth reconstruction. All teeth pulled, jaw drilled out, implants installed. = $40,000 to $60,000. Which "is not covered by health insurance, because it's cosmetic" ...riiiight.
Yea, yellow teeth are horrible, especially when a semi-hard piece of candy can make a piece break off if you bite wrong >.<