Translation of "Regretting" in Chinese

He is regretting his action.

他对他的行为感到后悔。

He was already regretting it.

他已经后悔了。

It's no use regretting it now.

現在後悔也沒用了。

I don't want to spend the rest of my life regretting it.

我不想让我的余生都活在后悔中。