used to be 造句?最好是易懂的..中文英文都要!

He used to be our monitor.
他以前当过我们的班长.
He used to be a team leader.
他干过队长.
He's much fatter than he used to be.
他比过去胖多了.
He used to be a dunce at school.
他上学时曾是个笨学生.
It used to be difficult to get drinking water here.
过去这里吃水很困难.
We used to be happier.
我们以前很快乐.