Teeth Whitening for Teeth with Thin Enamel?

I am a big fan of whitening. It is conservative and very effective as long as your teeth have enough enamel. The yellow part showing through is most likely the dentin and whitening is intended to work on the enamel portion.
For patients who have lost enamel to the degree that you are describing, then a restorative option becomes the best choice. That includes veneers, if there is enough enamel to achieve good bonding, but may mean full coverage all ceramic crowns for the best long term solution.
Remember that you are not only looking to improve the way you look, but you need to restore your function today and for your future.

As you have found out, whitening is not always the full answer. In your case I doubt it has done any harm, but if the colour is not what you were looking for, veneers are likely to be the best answer.You can go for composite veneers such as a product called Edelweiss, or a similar product from Coltene if your dentist provides it, or in office bonding of direct composite resins. Both are slightly cheaper but this is really a case if you get what you pay for. Good luck whatever you decide to do!Thomas Dey, BDS, MSc 

If your teeth are so eroded that the dentin shows through the translucent enamel on the front part of your teeth, you may have already lost all of the enamel on the back of your teeth. Whatever is left ( the dentin) will wear down much more quckly and will not bleach to a satisfactory shade
You should consider all porcelain crowns to restore the contour and color of your teeth, and protect them from further breakdown.