Weird... I can't ever remember having a garden where is didn't have tons of earth worms. Even in North Carolina where my garden was red clay, I still had tons of earth worms.
I really don't know why you don't have any... I suppose you could try and farm some to add to your garden. I did that when I was a kid and sold them by the dozen to fishermen. You can grow a lot of night crawlers in a 4' x 4' x 12" deep wooden box. I had mine down in the basement of our old house where it was cool. I farmed them in the winter and sold them in the spring and summer. I suppose you could farm them this winter then dump them in your garden this spring.
You don't happen to have a lot of moles do you? Moles eat worms and bugs in the ground.