What should I do with such feelings?

Sometimes, really, the more you care, the more you will get hurt. He may also want you to live in peace with him. But sometimes, boys are like this, maybe everyone is like this. There will be some nostalgia for their past feelings, especially the love that has not been separated because of subjective reasons. Give him some space. If you really love him, don't make yourself too tired and sad. His heart and his people are still yours. For a knowledgeable and rational adult like him, he should understand. Now you are the person he should cherish most.