im not sure what is causing this but perhaps try a floride mouthwash? and calcium suplements I think you should talk to a dentist about it too.

I already do/take both

ive heard of this condition befor but i dont really know what to tell you. I would ask my dentist if i were you. it would put your mind to rest.

my mind to rest?

what the...

forget about my mind... I want my teeth to look nice

Two possible things it could be are:

1. Bleaching your teeth - can cause them to have a more transparent look to them and it usually goes back if you stop whitening so much.

2. Grinding. A lot of people grind their teeth at night but have no idea they do it. The tops of the back teeth wear into the backside of the top teeth therefore thinning them out. A nightguard would help keep you from wearing into them more if this is the cuase but won't stop you from grinding. There are usually visible wear on the teeth in certain areas your dentist could check for...you coudl also check yourself and see if your teeth look more flat...esp the canines which are normally pretty pointed.