How to know if you're losing enamel or if your teeth are just yellow in som!

You would need a good toothpaste that contains fluoride. Just because the teeth is yellow does not necessarily mean that it is loosing enamel. If your loosing enamel the color would be white and not yellow. But as you brush with toothpaste that contain fluoride this should help out a lot.

Former dental assistant.

The area of enamel near the gum is very thin and can wear easily with tooth brushing.
Try maybe a toothpaste for sensitive teeth. It could be tar ta build up. If you are feeling sensitivity you may have wear of the enamel of you teeth and need to see a dentist to get the problem addressed.

Former Clinical manager of a cosmetic dental sugery.

It doesn't sound like it. It sound like just tarter build up. Always brush throughly 2-3 times a day. Floss daily, and use a tarter,enamel,etc rinse. Wal-Mart has one in a purple color for less than $3.00. Get a yearly cleaning/check up. Most people including myself don't have dental coverage and pay out of pocket. I go once a year. I paid last year $150. and I think that is high and just scheduled my yearly appt. for this March and it is now for the same thing....$210. It is the going fee. I get ripped off, but you need to go to catch other pricey things that can happen like a root canal.