请问“我已经注意你很久了”怎么翻译？

I have been noticing you for a long time.
为了表示已经，和动作现在仍在延续，需要用现在完成进行时。

I have noticed you for a long time.

I've been noticing you for quite a long time.

I have been watching you for a long time

是不是写情书用的？楼上比较对。