Are you stashing your money in your vault? You should keep as little money exposed as possible ... and increase the size of your vault as needed. Also, spend all your money on units rather than holding it for expansions or more buildings. The more units you have, the less inviting a target you'll be. You'll also have a better chance of minimizing the damage from an attack or even repelling it.
While your unit count is small, you can expect frequent attacks. As the count increases, fewer rivals will choose to attack. In the meantime, just keep that money in your vault and spend as much as you can adding units.