I'm at a loss for words.

我无言以对.




I'm speechless.

我讲不出话来.




I don't know what to say.

我不知该说什么.




I'm flabbergasted.

我目瞪口呆.




Words fail me to describe my feelings.

我的感受非言语所能形容.




I'm dumbstruck.

我不知该说些什么.