As an adult, I've just never had that many cavities. Dentists would compliment me on my teeth all the time. But as soon as I started going to this one dentist, it was like I suddenly had new cavities every visit. Over the course of a year, he found 4 new cavities and drilled them all (and for the record, every one of those fillings gave me trouble). Then, when I started going to a different dentist, the cavities suddenly stopped appearing again. It was like magic.
I wish I had my old x-rays. It would be interesting to review them and see what was actually there.