What if my ex-boyfriend sends me a text message after breaking up?

See what he means by sending it, whether he wants to make up with you or just say hello. If you still miss him, give him a hint or say hello directly. If you don't want to contact him, make it clear that you don't want to contact him, or handle it at will. Ordinary people who are very polite had better understand what it means. I think as long as you feel comfortable, don't think too much, happiness is the most important thing.