Sorry for / about -ING is used to refer to past things that one regrets. That-clauses are also very common in an informal style.
- I'm sorry for losing my temper this morning.
- I'm sorry about losing my temper this morning.
- I'm sorry that I lost my temper.
More formally,
sorry +
perfect infinitive can be used with the same meaning.
- I'm sorry to have woken you up.= I'm sorry that I woke you up.
Sorry +
infinitive is used to apologise for current situations – things that one is doing or going to do, or that one has just done.
- Sorry to disturb you – could I speak to you for a moment?
- I'm sorry to tell you that you failed the exam.
- Sorry to keep you waiting – we can start now.