Guys I need some advice.

So I got out of a FWB thing like two weeks ago. We were super close friends (basically grew up together) and a lot of our families called us the siblings we didn't have. (both single children) We had spent a lot of time together and became closer and then closer. He was my first everything. Kiss, sex, all of it. So needless to say, I'm pretty attached. But he called things off and made me promise to keep in touch but less then a week later I see him posting about a girl he helped move out, keep in mind he never posted about me cause of our families, but to see him kissing her cheek and hugging her all the time. And like a month ago we had talked about when I turn 18 he wants to have a future with me. Even if it was just dating he wanted to give it a try. But I don't think I can talk to him or even face him again. But he was only a FWB so I feel like I'm overreacting. But he was the first guy I ever loved. He was my best friend but I honestly loved him, so I just don't know what to do. Cause I can't see him happy with another girl. It would crush me. So what should I do, cause I just don't know.