How to recover after a denial?

I am 15m. I told my best female friend (3 years) that I love her for 3 years. She told me that she doesn’t love me as a bf but a bff. We are staying friends. She is a little cold to me because I told her that it would be better for me to recover. The first day I cried and I was lovesick. I losted my appetite, felt like shit and was sleepy. Today I am better. We act like nothing has happened. I still think about her and can’t laugh.

What are your suggestions? Please help me.