This is really a very sad thing. I like him very much, but he doesn't like himself. In fact, there are only two things you have to do at this time. Either you give him up and never like him again. Naturally, there won't be too many troubles and things that make you sad. Then the second thing is to continue to like her and impress her with your love, which may produce long-term feelings, but it is still risky. He may still dislike you under your fierce attack on her, or under the constant attack, then you may continue to be sad until then. If it is my choice, I may prefer the first choice, because after all, it is better to have a long pain than a short pain. When I cut the gordian knot, I can end this feeling as soon as possible and make myself less sad.
If you choose the first case, choose to give up directly. Then you don't have to think too much at all. As long as you stop thinking about him and liking him, there will be no subsequent development and entanglement between two people. This is actually a method that I personally admire, because it can cause less trouble, because I am particularly afraid of trouble. If you don't like me, forget it. I don't like you either. The world is so big and there are so many people. Why should I hang myself from your tree? Don't you think so?
However, if you choose the second method and choose long-term love, please stick to it, because it is not easy to like someone. When you meet someone, don't let go, don't let this opportunity flow away in vain.