How is your calcium intake? Or rather, your mineral balance? Your teeth are alive, just like your bones, and your body will redistribute calcium as it sees fit. You need to have sufficient calcium in your saliva, which lays calcium down on your tooth surface. Or so I understand. Not an expert.
I agree with the tooth soap idea. Am trying to wean myself from toothpaste, could not find one that doesn't have glycerin.
I use a tooth powder at least once/day. Toothpaste the other times. That's the best I can do right now.