Here's the super-condensed explanation (though a proper lesson would make it clear to you): "used to" = only in the past. It's a past habit or regular action. "be used to" = to be accustomed to; to find something as normal or familiar (although it was not so in the past). This is a state. "get used to" = this is a process; moving from finding something unfamiliar, to finding it normal and familiar. To become accustomed to something.