I've coming up here night after night for several weeks

这是现在完成进行时,给你个教程吧.
现在完成进行时的用法：
1）和现在完成时一样,现在完成进行时可以表示一个由过去某时开始一直持续到现在的动作,常和一个表示一段时间的状语一道用：
I have been learning English for two,years.（I am still learningnow．）
John has been teaching for 20 days．（He is still teaching．）They have been working since early morning．
He has been staying with his uncle during the past two months．I have been waiting all the morning（or this half hour）．表示暂时性的动作用完成进行时较好,表示长时期的动作时,用完成时较好：
I have lived here all my life．
We have developed our coundtry for two centuries.
2）和现在完成时一样,这个时态也可表示一个过去的动作对现在的影响：
I have been attending to many matters．（I am feeling tirednow．）
I have been telling him not to be a fool．（He should be cleverernow．）

have+完成式+动词ing
这个语法表示已经开始一段
时间的某个动作，并且正在持续
也就是说某个动作已经开始了
然后现在也还在进行，并且
有可能将来还要继续！

楼上说的好。这叫先在完成进行时。
I have been studying English day after day for three years.我一天接一天地学习英语已经有三年了。