Heart break- Help (very long)

He and I have been friends for almost three years, and this last year I knew that I liked him, but I hadn’t expressed anything because his best friend liked me last year and didn’t want them to argue.

He was always there for me, a shoulder to cry on, he lifted my spirit and was always nice and sincere. You could call him the perfect boy.

Two weeks ago he and his best friend got into a bad fight. Then he started talking to me, differently, like in a more romantic way. That continued and I fell in love with him. But today he was cold, he had a common friend that he just had free time and nothing to pass it with... i got so hurt that I left school, I cried and cried, and then I posted a pic in insta saying: it hurts but it’s ok, I’m used to.

After he saw it he posted a pic saying: be mine and I’ll devote my life to you.

I wasn’t sure it was for me after what happened so I dm him this: I hope you are happy with her.

He told me thank you and that was the final blow.

Why lead me on if you love someone else. It hurts so much and I have exams and I can’t concentrate. The worst part is I’m sitting at the same desk with him in school. I can’t stop crying. And unfortunately I can’t hate him. Please help. What can I do? It’s the first time it hurts so much to lose someone.