英语语法疑惑啊I have caught a bad cold for a week and I can't get r

这个问题与时态关系不大,而是与结束性动词和延续性动词有联系.
英语中的动词根据其持续时间的长短,分为两类,一类叫结束性动词（也叫短暂性动词,非延续性动词）,该动作发生后马上结束,持续时间非常短,如 close,shut,open,go,leave,come,buy,join,catch 等等,这些动词肯定形式一般不跟一段时间连用.例如,你可以说,I closed the door.He has bought a bike.I have caught a bad cold.但你不能说,I closed the door for ten minutes.也不能说 I have caught a bad cold for a week.因为该动作不能延续这么长时间.
另一类动词叫延续性动词（也叫持续性动词）,该动作发生后,可以延续一段时间,如 be,have,work,play,live,know 等等.例句：I have had a bad cold for a week.He has been away for two days.I have known him for ten years.
我们学英语时受汉语影响,经常会把结束性动词与一段时间连用,只要注意是可以避免的,我们只要用相应的延续性动词替换就可以了.如果要说“我买这辆自行车已经三年了.”
错误说法是：I have bought this bike for three years.（这里不管你用什么时态,都是错的.）
正确说法有：I have had this bike for three years.I bought this bike three years ago .
另外,否定句也正确,因为否定句表示“该结束性动作不结束的状态”可以延续,
I haven't bought a bike for three years.(该句正确,但 the 换成了 a ）
明白了结束性动词和延续性动词的区别后,你就能看懂下列例句：
I studied English for ten years.（我过去学了十年英语.一般过去时,正确.）
I have studied English for ten years.（到现在为止我已经学了十年英语.现在完成时,正确.）
I had studied English for ten years before I studied abroad.（在我出国留学前,我已学了十年英语.had studied 过去完成时,正确.）
再来看你的提问,I have caught a bad cold for a week and I can't get rid of it.
一定要把 caught 改为 had 才正确.如果把 have 改成 had 是不正确的.
另一动词 know 是延续性动词,“知道,了解”这种状态可以延续.

"catch" a bad cold 这个catch是非持续性动词，感冒嘛，往往就那么一下不注意就得了:），不能用一段时间来修饰。参考改法： I caught a cold a week ago and I haven't got rid of it yet.
你举的后一个例子中的know是持续性的，“得知”之后，就一直“知道”这则消息了。...

不管什么时态，非延续性动词在肯定句中都不能跟段时间