used to be是“曾经是````”
如：He used to be a teacher.他曾经是老师.
was often是“过去总是````”
如：She was often play computer games.她以前总是打电脑游戏.
used to doing是“习惯于做`````”
如：Now I used to watching TV when I do homework.
现在我习惯于做作业时看电视.