Why would he do this to me?

I have a friend, and he kept trying to add me on facebook as a girl. That means he pretends to be a girl and try to talk to me on facebook. Everytime, he tried to look real as possible. Why can't he just talk to me directly with his real facebook or even in real life? I know he is shy, but I don't think this is right. Why would he do this? Last time, he pretended to be a girl and say I love you and other affectionate things to me. In the real life, he barely talks to me.