I couldn't help overhearing you.

我不小心听到你的话。

Sorry, I couldn't help overhearing.

对不起，我无意中听到的。

I couldn't help overhearing what they said.

我忍不住偷听了他们说的话。

Excuse me-i couldn't help overhearing what you said.

对不起，我不由自主地听见你们谈的事情了。

If I could just come in here. I couldn't help overhearing.

我可以插句话吗？我无意中听到。