Your question is very confusing but I will try to answer. If you were in love with this guy, then why you told him you love someone else?
Now that he told you he is in love with your friend, you are just afraid to lose him.
You have to think yourself and decide if you are in love with him or it is just a Crush or you like him because love is totally a different feeling.
Now the other part of the story, he is in love with your best friend. If that is true, I do not believe you want to lose your best friend.
You are in very sensitive situation therefore whatever step or steps you take. Just be careful not to hurt yourself or someone else feelings.
I tried my best to answer your question and I hope it is up to your satisfaction.
I wish you all the best.
~When I first saw you, I was afraid to talk to you. When I first talked to you, I was afraid to like you. When I first liked you, I was afraid to love you. Now that I love you, I am afraid to lose you. ~