I believe what you are describing are called "Tonsilloliths," which are defined as calcareous concretions in a distended tonsillar crypt. Try to take a look more closely and see if there are white balls hanging around in little pockets on your tonsils--there probably are.
They are the dead cells from your mouth--they get stuck in your tonsils and form up into little balls. It's a pain in the ass to get them out and a lot of people have them. Some people use q-tips to get them out, I use a pick that dentists use to pick off debris. Try to gargle with warm salt water and keep your mouth as clean as possible.
edit: sl83 beat me. But he's right, what you eat/drink may have only a little effect on it. I have noticed, however, that it gets worse when I eat foods that swell my throat such as sushi. Also, smoking pot can have an effect on it.
A lot of people have the fuckin things and you gotta live with em. Only for sure cure is to get your tonsils yanked.