What to text to win him back?

Read the gap before you read the message. If he went quiet mid-conversation without any explanation, he may just be overwhelmed or avoidant, and that is common and often not about you. If he told you directly that he was pulling back, he has already answered the question you are asking, and the honest read is that he needs distance right now. Her messages are not the subject here. What matters is whether his own words left a door open or closed it. Look at his last few messages for tone. Warm but vague means he may come back when the pressure drops. Flat and final means he has moved on for now. Your reply should fit whichever of those is true, not the version you hope for.

The reply that tends to work is short, specific, and points at something outside the breakup. A reference to a shared thing, a question he can answer in a sentence, or a light observation he would find funny all give him an easy yes. Aim for one sentence of warmth, one concrete hook, and no question that asks him to define the relationship. Leave out anything that mentions why it ended, anything that says you miss him in an intense way, and anything that asks why he did what he did. The test is simple: if he could answer with one word and feel fine, the draft is in the right range. If answering would feel like a confession, cut it down.

Timing matters more than wording. If you have not heard from him for more than a few days after a message, do not send another one that week. Give it a week or two before any follow-up, and make the follow-up even lighter than the first. If he replies warmly, match his energy and keep the next message small. If he replies short or cool, accept it and do not argue the point. If there is no answer after two messages spread over a few weeks, stop. Going past that turns a clean exit into a pattern he will remember, and it makes any future contact harder. Send your last message and let it sit.