This is same thing that happened to me. Exact same thing. I still value her so much. She was also ok so we have a lot of thing in common. We stayed as bestfriends for a long time. Let me say what will happen. One day he will find a girl and you will feel horrible, worse than today. She gave me more attention before a near time ago. This created a hope inside of me and I tried my chance again and you can make a guess whay happened :p. But she has a great relationship now. Everytime I see their couple pfp's I still feel bad but this badness level decreases day by day. I just suggest to set a distance between you and him but this is my oppinion and it releated to my experiences. Maybe your story will be different who know. Just be careful and take care of yourself. I didn't do that and I'm somewhere that you never want to be. Some actions that we need to take is not the thing what we want. Take care and don't let anyone make you feel not valuable.