If I want to say:
(1) Last night I didn't go to the concert, but I don't regret it. They told me that it was extremely boring
(2) I argued with him an extremely aggressive way, shouting and swearing. But I don't regret it. He is a real a..hole.
(3) I don't not regret for anything in my life. Even the mistakes taught me many things.
Until know I was using сожалеть but they told me that this a mistake and it means just feel sorry / pitty for someone. Correct?