I broke up with a boy before, and after a long time, he suddenly sent me a text message saying that he apologized for everything he had done before?

After reading your above description, you broke up with a boy before, and after a long time, he suddenly sent you a text message saying that he was sorry for everything he had done before.

I think you broke up with a boy before, and then after a long time, he suddenly sent you a text message saying that he was sorry for what he had done before. As you guessed, he must have been moved by something later, so he suddenly sent you a text message to apologize. Since you don't feel anything for him now, you can choose not to reply to him, just as if you didn't see it. Don't let it disturb your normal life.